Journal articles: 'Varying grain sizes'

1

Kuronen, Mikko, and Lasse Leskelä. "Hard-Core Thinnings of Germ‒Grain Models with Power-Law Grain Sizes." Advances in Applied Probability 45, no. 03 (September 2013): 595–625. http://dx.doi.org/10.1017/s0001867800006509.

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Random sets with long-range dependence can be generated using a Boolean model with power-law grain sizes. We study thinnings of such Boolean models which have the hard-core property that no grains overlap in the resulting germ‒grain model. A fundamental question is whether long-range dependence is preserved under such thinnings. To answer this question, we study four natural thinnings of a Poisson germ‒grain model where the grains are spheres with a regularly varying size distribution. We show that a thinning which favors large grains preserves the slow correlation decay of the original model, whereas a thinning which favors small grains does not. Our most interesting finding concerns the case where only disjoint grains are retained, which corresponds to the well-known Matérn type-I thinning. In the resulting germ‒grain model, typical grains have exponentially small sizes, but rather surprisingly, the long-range dependence property is still present. As a byproduct, we obtain new mechanisms for generating homogeneous and isotropic random point configurations having a power-law correlation decay.

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Kuronen, Mikko, and Lasse Leskelä. "Hard-Core Thinnings of Germ‒Grain Models with Power-Law Grain Sizes." Advances in Applied Probability 45, no. 3 (September 2013): 595–625. http://dx.doi.org/10.1239/aap/1377868531.

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Random sets with long-range dependence can be generated using a Boolean model with power-law grain sizes. We study thinnings of such Boolean models which have the hard-core property that no grains overlap in the resulting germ‒grain model. A fundamental question is whether long-range dependence is preserved under such thinnings. To answer this question, we study four natural thinnings of a Poisson germ‒grain model where the grains are spheres with a regularly varying size distribution. We show that a thinning which favors large grains preserves the slow correlation decay of the original model, whereas a thinning which favors small grains does not. Our most interesting finding concerns the case where only disjoint grains are retained, which corresponds to the well-known Matérn type-I thinning. In the resulting germ‒grain model, typical grains have exponentially small sizes, but rather surprisingly, the long-range dependence property is still present. As a byproduct, we obtain new mechanisms for generating homogeneous and isotropic random point configurations having a power-law correlation decay.

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Dhami, Navdeep Kaur, M. Sudhakara Reddy, and Abhijit Mukherjee. "Significant indicators for biomineralisation in sand of varying grain sizes." Construction and Building Materials 104 (February 2016): 198–207. http://dx.doi.org/10.1016/j.conbuildmat.2015.12.023.

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Månsson, Marianne, and Mats Rudemo. "Random patterns of nonoverlapping convex grains." Advances in Applied Probability 34, no. 04 (December 2002): 718–38. http://dx.doi.org/10.1017/s0001867800011885.

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Generalizing Matérn's (1960) two hard-core processes, marked point processes are considered as models for systems of varying-sized, nonoverlapping convex grains. A Poisson point process is generated and grains are placed at the points. The grains are supposed to have varying sizes but the same shape as a fixed convex grain, with spheres as an important special case. The pattern is thinned so that no grains overlap. We consider the thinning probability of a ‘typical point’ under various thinning procedures, the volume fraction of the resulting system of grains, the relation between the intensity of the point processes before and after thinning, and the corresponding size distributions. The study is inspired by problems in material fatigue, where cracks are supposed to be initiated by large defects.

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Månsson, Marianne, and Mats Rudemo. "Random patterns of nonoverlapping convex grains." Advances in Applied Probability 34, no. 4 (December 2002): 718–38. http://dx.doi.org/10.1239/aap/1037990950.

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Generalizing Matérn's (1960) two hard-core processes, marked point processes are considered as models for systems of varying-sized, nonoverlapping convex grains. A Poisson point process is generated and grains are placed at the points. The grains are supposed to have varying sizes but the same shape as a fixed convex grain, with spheres as an important special case. The pattern is thinned so that no grains overlap. We consider the thinning probability of a ‘typical point’ under various thinning procedures, the volume fraction of the resulting system of grains, the relation between the intensity of the point processes before and after thinning, and the corresponding size distributions. The study is inspired by problems in material fatigue, where cracks are supposed to be initiated by large defects.

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Sob, P. Baonhe, A. Alfayo Alugongo, and T. Ba Bob Tengen. "Stochastic Effect of Grain Elongation on Nanocrystalline Materials Strain and Strain Rate Produced by Accumulative Roll-Bonding and Equal Channel Angular Pressing." Advances in Materials Science and Engineering 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/5418769.

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Severe plastic deformation techniques are acknowledged to produce elongated grains during fabrication of nanostructured materials. Previous models relating grain size to mechanical properties considered only equivalent radius, thus ignoring other approaches of measuring grain sizes such as semiminor axis, semimajor axis, and major axis radii that determine true grain shape. In this paper, stochastic models of nanomaterials mechanical properties that include the ignored parameters have been proposed. The proposed models are tested with data from nanocrystalline aluminum samples. The following facts were experimentally observed and also revealed by the models. Grain elongates to a maximum value and then decreases with further grain refinement due to grain breakages. Materials yield stress increases with elongation to a maximum and then decreases continuously. The varying approaches of measuring grain radius reveal a common trend of Hall-Petch and Reverse Hall-Petch Relationship but with different critical grain sizes. Materials with high curvature grains have more enhanced yield stress. Reducing strain rates leads to materials with more enhanced yield stress, with critical strain rates values beyond which further reductions do not lead to yield stress enhancement. It can be concluded that, by considering different approaches of measuring grain sizes, reasons for different yield stress for nanomaterials that were observed but could not be explained have been dealt with.

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Lan, Liangyun, Zhiyuan Chang, and Penghui Fan. "Exploring the Difference in Bainite Transformation with Varying the Prior Austenite Grain Size in Low Carbon Steel." Metals 8, no. 12 (November 24, 2018): 988. http://dx.doi.org/10.3390/met8120988.

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The simulation welding thermal cycle technique was employed to generate different sizes of prior austenite grains. Dilatometry tests, in situ laser scanning confocal microscopy, and transmission electron microscopy were used to investigate the role of prior austenite grain size on bainite transformation in low carbon steel. The bainite start transformation (Bs) temperature was reduced by fine austenite grains (lowered by about 30 °C under the experimental conditions). Through careful microstructural observation, it can be found that, besides the Hall–Petch strengthening effect, the carbon segregation at the fine austenite grain boundaries is probably another factor that decreases the Bs temperature as a result of the increase in interfacial energy of nucleation. At the early stage of the transformation, the bainite laths nucleate near to the grain boundaries and grow in a “side-by-side” mode in fine austenite grains, whereas in coarse austenite grains, the sympathetic nucleation at the broad side of the pre-existing laths causes the distribution of bainitic ferrite packets to be interlocked.

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Mattsson, L., J. P. U. Fynbo, and B. Villarroel. "Small-scale clustering of nano-dust grains in supersonic turbulence." Monthly Notices of the Royal Astronomical Society 490, no. 4 (October 24, 2019): 5788–97. http://dx.doi.org/10.1093/mnras/stz2957.

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ABSTRACT We investigate the clustering and dynamics of nano-sized particles (nano dust) in high-resolution (10243) simulations of compressible isothermal hydrodynamic turbulence. It is well established that large grains will decouple from a turbulent gas flow, while small grains will tend to trace the motion of the gas. We demonstrate that nano-sized grains may cluster in a turbulent flow (fractal small-scale clustering), which increases the local grain density by at least a factor of a few. In combination with the fact that nano-dust grains may be abundant in general, and the increased interaction rate due to turbulent motions, aggregation involving nano dust may have a rather high probability. Small-scale clustering will also affect extinction properties. As an example we present an extinction model based on silicates, graphite, and metallic iron, assuming strong clustering of grain sizes in the nanometre range, could explain the extreme and rapidly varying ultraviolet extinction in the host of GRB 140506A.

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Kamatar, Vishwanath S., Rajesh Yakkundimath, and Girish Saunshi. "Behavior of SVM based classification for varying sizes of heap-grain images." International Journal of Computer Sciences and Engineering 6, no. 12 (December 31, 2018): 32–42. http://dx.doi.org/10.26438/ijcse/v6i12.3242.

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Cheng, Hong, Chenchen Liu, Xueyong Zou, Jifeng Li, Jiajia He, Bo Liu, Yongqiu Wu, Liqiang Kang, and Yi Fang. "Aeolian creeping mass of different grain sizes over sand beds of varying length." Journal of Geophysical Research: Earth Surface 120, no. 7 (July 2015): 1404–17. http://dx.doi.org/10.1002/2014jf003367.

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11

Phaneesh, Kalale Raghavendra Rao, Anirudh Bhat, Gautam Mukherjee, and Kishore T. Kashyap. "Effect of Particle Size on the Zener Limit: A Monte Carlo Simulation Approach." Advanced Materials Research 560-561 (August 2012): 152–55. http://dx.doi.org/10.4028/www.scientific.net/amr.560-561.152.

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2D Potts model Monte Carlo simulation was carried out on a square lattice to investigate the effects of varying the size of second phase particles on the Zener limit of grain growth, in two-phase polycrystals. Simulations were carried out on a 1000^2 size matrix with Q-state of 64, dispersed with second phase particles of various sizes and surface fractions, and run to stagnation. Different grain growth parameters such as mean grain size, largest grain size, fraction of second phase particles lying on grain boundaries, etc., were computed for the pinned microstructures. The pinned average grain size or the Zener limit increased with increase in particle size, as per the classic Smith-Zener equation. The Zener limit scaled inversely with the square root of the particle fraction for all particle sizes, while it scaled exponentially with the fraction of second phase particles lying on the grain boundaries (ϕ), for all particle sizes tested.

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Kirchschlager, Florian, and Gesa H. M. Bertrang. "Self-scattering of non-spherical dust grains." Astronomy & Astrophysics 638 (June 2020): A116. http://dx.doi.org/10.1051/0004-6361/202037943.

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Context. The understanding of (sub-)millimetre polarisation has made a leap forward since high-resolution imaging with the Atacama Large (sub-)Mm Array (ALMA) became available. Amongst other effects, self-scattering (i.e. the scattering of thermal dust emission on other grains) is thought to be the origin of millimetre polarisation. This opens the first window to a direct measurement of dust grain sizes in regions of optically thick continuum emission as it can be found in protoplanetary discs and star-forming regions. However, the newly derived values of grain sizes are usually around ~100 μm and thus one order of magnitude smaller than those obtained from more indirect measurements, as well as those expected from theory (~1 mm). Aims. We see the origin of this contradiction in the applied dust model of current self-scattering simulations: a perfect compact sphere. The aim of this study is to test our hypothesis by investigating the impact of non-spherical grain shapes on the self-scattering signal. Methods. We applied discrete dipole approximation simulations to investigate the influence of the grain shape on self-scattering polarisation in three scenarios: an unpolarised and polarised incoming wave under a fixed and a varying incident polarisation angle. Results. We find significant deviations of the resulting self-scattering polarisation when comparing non-spherical to spherical grains. In particular, tremendous deviations are found for the polarisation signal of grains when observed outside the Rayleigh regime, that is for >100 μm sized grains observed at the 870 μm wavelength. Self-scattering by oblate grains produces higher polarisation degrees compared to spheres, which challenges the interpretation of the origin of observed millimetre polarisation. A (nearly) perfect alignment of the non-spherical grains is required to account for the observed millimetre polarisation in protoplanetary discs. Furthermore, we find conditions under which the emerging scattering polarisation of non-spherical grains is flipped in orientation by 90°. Conclusions. These results show clearly that the perfect compact sphere is an oversimplified model, which has reached its limit. Our findings point towards a necessary re-evaluation of the dust grain sizes derived from (sub-)millimetre polarisation.

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13

Dai, Y. Z., and F. P. Chiang. "On the Mechanism of Plastic Deformation Induced Surface Roughness." Journal of Engineering Materials and Technology 114, no. 4 (October 1, 1992): 432–38. http://dx.doi.org/10.1115/1.2904196.

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The plastic deformation induced surface roughening mechanism of aluminum sheets is experimentally investigated. Specimens used in the study have grain sizes varying from tens of microns to millimeters. The roughnesses of the specimens’ free surfaces are measured during plastic deformation by means of a mechanical stylus type profilometer with a tip radius of 5 microns. Observations show that plastic deformation roughens a free surface mainly by introducing slip bands within individual grains and relative rotation among grains. The average grain rotation and grain size are found to be the dominant contributor to the surface vertical characteristics such as the root-mean-square roughness. The surface horizontal characteristic such as the correlation length is found to be mainly determined by the average grain size. Based on the observations and some analysis, a model is advanced for the explanation of the phenomenon that the root-mean-square roughness is proportional to the magnitude of plastic deformation and average grain size.

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14

Tobin, G., E. McGlynn, M. O. Henry, J. P. Mosnier, J. G. Lunney, D. O’Mahony, and E. dePosada. "Ultraviolet stimulated emission from bulk and polycrystalline ZnO thin films with varying grain sizes." Physica B: Condensed Matter 340-342 (December 2003): 245–49. http://dx.doi.org/10.1016/j.physb.2003.09.016.

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15

Capdevila, Carlos, Tommy De Cock, Francisca García Caballero, Carlos García-Mateo, and Carlos García de Andrés. "Evaluation of the Austenitic Grain Growth by Thermoelectric Power Measurements." Materials Science Forum 467-470 (October 2004): 863–68. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.863.

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The influence of the deformation grade on the recrystallised grain size has been studied in the AISI 304 stainless steel. Therefore, cold rolled samples of this material with reductions varying between 30% and 80% were annealed at different temperatures and subsequently quenched. The mean austenitic grain sizes were measured and compared. Moreover, the correlation between the variation of the thermoelectric power and the grain growth was investigated for each degree of prior deformation.

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16

Priedeman, Jonathan L., Brandon J. Phillips, Jessica J. Lopez, Brett E. Tucker Roper, B. Chad Hornbuckle, Kristopher A. Darling, J. Brian Jordon, Paul G. Allison, and Gregory B. Thompson. "Microstructure Development in Additive Friction Stir-Deposited Cu." Metals 10, no. 11 (November 19, 2020): 1538. http://dx.doi.org/10.3390/met10111538.

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This work details the additive friction stir-deposition (AFS-D) of copper and evaluation of its microstructure evolution and hardness. During deposition, a surface oxide is formed on the deposit exterior. A very fine porosity is formed at the substrate–deposit interface. The deposit (four layers of 1 mm nominal height) is otherwise fully dense. The grains appear to have recrystallized throughout the deposit with varying levels of refinement. The prevalence of twinning was found to be dependent upon the grain size, with larger local grain sizes having a higher number of twins. Vickers hardness measurements reveal that the deposit is softer than the starting feedstock. This result indicates that grain refinement and/or higher twin densities do not replace work hardening contributions to strengthen Cu processed by additive friction stir-deposition.

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Piot, David, Guillaume Smagghe, and Frank Montheillet. "Modeling of Grain-Boundary Mobility and Nucleation Rate during Discontinuous Dynamic Recrystallization in Ni-Nb Alloys and a High-Purity Alloy Derived from SAE 304L." Materials Science Forum 879 (November 2016): 1501–6. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1501.

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A simple mesoscale model has been developed for discontinuous dynamic recrystallization. Each grain is considered in turn as an inclusion, embedded in a homogeneous equivalent matrix, the properties of which are obtained by averaging over all the grains. The model includes: (i) a grain-boundary migration-equation driving the evolution of grain size via the mobility of grain boundaries, which is coupled with (ii) a single-internal-variable (dislocation density) constitutive model for strain hardening and dynamic recovery, and (iii) a nucleation equation governing the total number of grains by the nucleation of new grains. All the system variables tend to asymptotic values at large strains, in agreement with the experimentally observed steady-state regime.With some assumptions, both steady-state stress and grain-size are derived in closed forms, allowing immediate identification of the mobility of grain boundaries and the rate of nucleation. An application to Ni–Nb-pure-binary model alloys and high-purity 304L stainless steel with Nb addition is presented. More specifically on one hand, from experimental steady-state stresses and grain sizes, variations of the grain boundary mobility and the nucleation rate with niobium content are addressed in order to quantify the solute-drag effect of niobium in nickel. And on the other hand, the Derby exponents were investigated varying separately the strain rate or the temperature.

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Tengen, T. B., Tomasz Wejrzanowski, R. Iwankiewicz, and Krzysztof Jan Kurzydlowski. "Statistical Model of Grain Growth in Polycrystalline Nanomaterials." Solid State Phenomena 129 (November 2007): 157–63. http://dx.doi.org/10.4028/www.scientific.net/ssp.129.157.

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Nanomaterials, due to their fine grain sizes, exhibit enhanced mechanical properties. However, their low stability at also relatively low temperatures might limit their future applications. In the present work, a statistical model has been proposed in order to study grain growth processes in nanomaterials. The Hillert’s approach has been extended by incorporating two mechanisms of growth for an individual grain: grain boundary migration – GBM - (diffusion based - continuous) and grain-rotation coalescence – GRC - (discontinuous). The influence of the grain size distribution on the grain growth process has been studied. The results show that the inclusion of GRC mechanisms results in a departure from the parabolic law of grain growth. Such a deviation has also been observed experimentally, especially in nanomaterials. The results reveal that grain growth rate increases with higher dispersion of the fine grains and the rotation mechanism can initiate growth even with low dispersion. This causes a steady increase in the coefficient of variation which, after some time interval, decays to homogeneity. This paper also demonstrates that the average rotation mobility which is a consequence of the varying misorientation angle contributes up to about 50% of the overall average boundary mobility.

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Olabisi, Adeyemi I., Thankgod E. Boye, and Emagbetere Eyere. "Evaluation of Pure Aluminium Inoculated with Varying Grain Sizes of an Agro-waste based Inoculant." Advances in Science, Technology and Engineering Systems Journal 2, no. 4 (April 2017): 14–25. http://dx.doi.org/10.25046/aj020403.

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Ahn, Namyoung, Seong Min Kang, Jin-Wook Lee, Mansoo Choi, and Nam-Gyu Park. "Thermodynamic regulation of CH3NH3PbI3crystal growth and its effect on photovoltaic performance of perovskite solar cells." Journal of Materials Chemistry A 3, no. 39 (2015): 19901–6. http://dx.doi.org/10.1039/c5ta03990h.

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We report a theoretical analysis on the crystallization of CH₃NH₃PbI₃and the control of grain sizes by varying the two-step reaction temperature from −10 °C to 50 °C based on the present analysis.

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Freitas, Antonio E., Taise M. Manhabosco, Ronaldo J. C. Batista, Alan K. Rêgo Segundo, Humberto X. Araújo, Fernando Gabriel S. Araújo, and Adilson R. Costa. "Development and Characterization of Titanium Dioxide Ceramic Substrates with High Dielectric Permittivities." Materials 13, no. 2 (January 14, 2020): 386. http://dx.doi.org/10.3390/ma13020386.

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Titanium dioxide substrates have been synthesized by means of solid-state reactions with sintering temperatures varying from 1150 °C up to 1350 °C. X-ray diffraction and scanning electron microscopy (SEM) where employed to investigate the crystal structure, grain size and porosity of the resulting samples. The obtained ceramics are tetragonal (rutile phase) with average grain sizes varying from 2.94 µm up to 5.81 µm. The average grain size of samples increases with increasing temperature, while the porosity decreases. The effect of microstructure on the dielectric properties has been also studied. The reduction of porosity of samples significantly improves the dielectric parameters (relative dielectric permittivity and loss tangent) in comparison to those of commercial substrates, indicating that the obtained ceramic substrates could be useful in the miniaturization of telecommunication devices.

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HAAVIK, C., E. OTTESEN, K. NOMURA, J. KILNER, and T. NORBY. "Temperature dependence of oxygen ion transport in Sr+Mg-substituted LaGaO (LSGM) with varying grain sizes." Solid State Ionics 174, no. 1-4 (October 29, 2004): 233–43. http://dx.doi.org/10.1016/j.ssi.2004.07.033.

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Park, E. T., P. Nash, J. Wolfenstine, K. C. Goretta, and J. L. Routbort. "High-temperature creep of polycrystalline BaTiO3." Journal of Materials Research 14, no. 2 (February 1999): 523–28. http://dx.doi.org/10.1557/jmr.1999.0075.

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Compressive creep of dense BaTiO3 having linear-intercept grain sizes of 19.3–52.4 μm was investigated at 1200–1300 °C by varying the oxygen partial pressure from 102 to 105 Pa in both constant-stress and constant-crosshead-velocity modes. Microstructures of the deformed materials were examined by scanning and transmission electron microscopy. The stress exponent was ≈1, the grain-size dependence was ≈1/d2, and the activation energy was ≈720 kJ/mole. These parameters, combined with the microstructural observations (particularly grain displacement and absence of deformation-induced dislocations), indicated that the dominant deformation mechanism was grain-boundary sliding accommodated by lattice cation diffusion. Because of the absence of an oxygen partial pressure dependence, diffusion was probably controlled extrinsically.

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Lebreuilly, U., B. Commerçon, and G. Laibe. "Protostellar collapse: the conditions to form dust-rich protoplanetary disks." Astronomy & Astrophysics 641 (September 2020): A112. http://dx.doi.org/10.1051/0004-6361/202038174.

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Context. Dust plays a key role during star, disk, and planet formation. Yet, its dynamics during the protostellar collapse remain a poorly investigated field. Recent studies seem to indicate that dust may decouple efficiently from the gas during these early stages. Aims. We aim to understand how much and in which regions dust grains concentrate during the early phases of the protostellar collapse, and to see how this depends on the properties of the initial cloud and of the solid particles. Methods. We used the multiple species dust dynamics MULTIGRAIN solver of the grid-based code RAMSES to perform various simulations of dusty collapses. We performed hydrodynamical and magnetohydrodynamical simulations where we varied the maximum size of the dust distribution, the thermal-to-gravitational energy ratio, and the magnetic properties of the cloud. We simulated the simultaneous evolution of ten neutral dust grain species with grain sizes varying from a few nanometers to a few hundreds of microns. Results. We obtain a significant decoupling between the gas and the dust for grains of typical sizes of a few tens of microns. This decoupling strongly depends on the thermal-to-gravitational energy ratio, the grain sizes, and the inclusion of a magnetic field. With a semi-analytic model calibrated on our results, we show that the dust ratio mostly varies exponentially with the initial Stokes number at a rate that depends on the local cloud properties. Conclusions. We find that larger grains tend to settle and drift efficiently in the first-core and in the newly formed disk. This can produce dust-to-gas ratios of several times the initial value. Dust concentrates in high-density regions (cores, disk, and pseudo-disk) and is depleted in low-density regions (envelope and outflows). The size at which grains decouple from the gas depends on the initial properties of the clouds. Since dust cannot necessarily be used as a proxy for gas during the collapse, we emphasize the necessity of including the treatment of its dynamics in protostellar collapse simulations.

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Winter, Thomas, Richard Hoffman, and Chaitanya S. Deo. "Grain Subdivision Fission Gas Swelling Model for UO2." MRS Advances 1, no. 35 (2016): 2465–70. http://dx.doi.org/10.1557/adv.2016.497.

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ABSTRACTUnder high burnup UO2 fuel pellets can experience high burnup structure (HBS) at the rim also known as rim effect. The HBS is exceptionally porous with fine grain sizes. HBS increases the swelling further than it would have achieved at a larger grain size. A theoretical swelling model is used in conjunction with a grain subdivision simulation to calculate the swelling of UO2. In UO2 the nucleation sites are at vacancies and the bubbles are concentrated at grain boundaries. Vacancies are created due to irradiation and gas diffusion is dependent on vacancy migration. In addition to intragranular bubbles, there are intergranular bubbles at the grain boundaries. Over time as intragranular bubbles and gas atoms accumulate on the grain boundaries, the intergranular bubbles grow and cover the grain faces. Eventually they grow into voids and interconnect along the grain boundaries, which can lead to fission gas release when the interconnection reaches the surface. This is known as the saturation point. While the swelling model used does not originally incorporate a changing grain size, the simulation allows for more accurate swelling calculations by introducing a fractional HBS based on the temperature and burnup of the pellet. The fractional HBS is introduced with a varying grain size. Our simulations determine the level of swelling and saturation as a function of burnup by combining an independent model and simulation to obtain a more comprehensive model.

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Jung, Woo Young, and Tae Kwon Ha. "High Temperature Deformation Behavior of 8090 Al-Li Alloy." Advances in Materials Science and Engineering 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/512606.

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High temperature deformation behavior, especially the superplasticity of an 8090 Al-Li alloy, was studied within the recent framework of the internal variable theory of structural superplasticity. In this study, a series of load relaxation tests were conducted at various temperatures ranging from 200°C to 530°C to obtain the flow curves of log ε˙versus log ε. The effect of grain size was also examined by varying the grain sizes through a proper thermomechanical treatment. The flow curves were found to be composite curves consisting of contributions from grain boundary sliding (GBS) and grain matrix deformation (GMD) at superplastic temperatures. The activation energy obtained for GMD was 124.9 kJ/mole in the temperature range from 470°C to 530°C, very similar to that for self-diffusion in pure Al.

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Qiao, Jiaolong, Chuanxing Liu, Feihu Guo, Li Xiang, Shengtao Qiu, and Haijun Wang. "Effect of recrystallization annealing temperature on texture and magnetic properties of 2.97% Si non-oriented silicon steel." Metallurgical Research & Technology 116, no. 4 (2019): 412. http://dx.doi.org/10.1051/metal/2018123.

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The effect of recrystallization annealing at temperatures varying from 910 to 1060 °C on the texture and magnetic properties of cold-rolled sheets with 0.3 mm in thickness of 2.97 wt.% Si–0.59wt.% Al non-oriented silicon steel were investigated. With increasing of cold-rolled sheets annealing temperature, the average of the recrystallized grain sizes increased, because of higher temperature corresponds to a faster migration rate of grain boundaries. Increasing of grain size resulted in reducing of the hysteresis loss and core losses, as the number of grain boundary significantly reduced. However, the domain size and the eddy current loss would increase as the grain sizes continued to increase, and then affecting the core losses. The oversized microstructure (∼140 µm) in 1030 °C annealed sheet brought about an augment in P15/50 (∼2.27 W/kg) and (∼130 µm) in 1000 °C annealed sheet of P10/400 (∼12.84 W/kg). Furthermore, the textures of the final sheets were mainly made up of α*-fiber, γ-fiber and {001}<130> texture. The magnetic induction diminished with increasing of annealing temperature and this result could be attributed to the strengthening in γ-fiber (<111>//ND) and weakening in λ-fiber (<100>//ND) texture.

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28

Allen, Carol. "Details of Thin Section Analysis of Pottery Fabrics." Proceedings of the Prehistoric Society 53, S3 (1987): 53–59. http://dx.doi.org/10.1017/s0079497x00078774.

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Terms usedGrog relates to clay inclusions within the pottery which appear as discrete pieces of varying sizes. Usually such entities are assumed to be crushed parts of pre-existing pots.Sizes of quartz, grog, shell or other inclusions referred to in the analysis concern measurements taken on the longest axis of the grain or piece. In each case the maximum measurement stated is the longest observed in that particular section, and does not infer that other grains in the sample were all of this size, unless stated.Percentages of materials shown as included in the clay matrix are estimates expressed by area using comparison charts (Terry and Chilingar 1955, and Flugel 1982, 247-257).

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Ysard, N., A. P. Jones, K. Demyk, T. Boutéraon, and M. Koehler. "The optical properties of dust: the effects of composition, size, and structure." Astronomy & Astrophysics 617 (September 2018): A124. http://dx.doi.org/10.1051/0004-6361/201833386.

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Context. Dust grains are determinant for setting the chemical, physical, dynamical, and radiative properties of all the media in which they are present. Their influence depends on the grain composition, size, and geometrical structure which vary throughout the life cycle of dust. In particular, grain growth arises in dense molecular clouds and protoplanetary disks as traced by an enhancement of the dust far-IR emissivity and by the effects of cloudshine and coreshine. Aims. Our aim is to investigate the imprint of the grain characteristics on the dust unpolarised optical properties from the visible to the far-IR wavelengths for isolated grains as well as for aggregates. Methods. Using optical constants for both carbonaceous and silicate materials, we have derived the absorption and scattering efficiencies, the asymmetry factor of the phase function, the single scattering albedo, and the mass opacity for isolated grains and aggregates, using either the Mie theory or the discrete dipole approximation (DDA). We investigated the effects of the size, porosity, and shape of the grains, and of the monomers constituting the aggregates, on the optical properties. Besides this, for aggregates we studied the influence of the number of monomers and of mixing monomer sizes. Results. Grain structure changes result in optical property variations at all wavelengths. Porosity, grain elongation, as well as aggregation all produce an increase in the far-IR opacity. The spectral dependence of this increase depends on the nature of the material composing the grain: it is independent of the wavelength for insulators but not for conductors. In the case of aggregates, the far-IR increase does not depend on the monomer size and saturates for aggregates containing six or more monomers. In the visible and near-IR, the aggregate behaviour is reminiscent of a compact sphere of the same mass whereas at longer wavelengths, it is closer to the effect of porosity. Finally, for silicates, the mid-IR spectral feature at 18 μm is more sensitive to the details of the grain structure than the 10 μm feature. Conclusions. Dust optical properties, from the visible to the far-IR, are highly dependent upon the grain composition, size, and structure. This study provides a basis for understanding the range of variations achievable as a result of varying the grain characteristics. It emphasises the importance of considering the detailed grain structure in determining the dust optical properties and of using exact methods because approximate methods cannot reproduce the entire range of the observed variations at all wavelengths.

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Wei, Anran, Qihao Liu, Haimin Yao, Ye Li, and Yinfeng Li. "Principles and Mechanisms of Strain-Dependent Thermal Conductivity of Polycrystalline Graphene with Varying Grain Sizes and Surface Hydrogenation." Journal of Physical Chemistry C 122, no. 34 (August 9, 2018): 19869–79. http://dx.doi.org/10.1021/acs.jpcc.8b03393.

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Papet, Philippe, Joseph P. Dougherty, and Thomas R. Shrout. "Particle and grain size effects on the dielectric behavior of the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3." Journal of Materials Research 5, no. 12 (December 1990): 2902–9. http://dx.doi.org/10.1557/jmr.1990.2902.

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The role of particle and grain size on the dielectric behavior of the perovskite relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 [PMN] was investigated. Ultrafine powders of PMN were prepared using a reactive calcination process. Reactive calcination, the process by which morphological changes take place upon reaction of the component powders, produced particle agglomerates less than 0.5 μm. Through milling, these structures were readily broken down to ∼70 nanometer-sized particulates. The highly reactive powders allowed densification as low as 900 °C, but with corresponding grain growth in the micron range. Such grain growth was associated with liquid phase sintering as a result of PbO–Nb2O5 second phase(s) pyrochlore. Sintering, assisted by hot uniaxial pressing, below the temperature of liquid formation of 835 °C, allowed the fabrication of highly dense materials with a grain size less than 0.3 μm. The dielectric and related properties were determined for samples having grain sizes in the range of 0.3 μm to 6 μm. Characteristic of relaxors, frequency dependence (K and loss) and point of Tmax were found to be related to grain and/or particle size and secondarily to the processing conditions. Modeling of particle size/dielectric behavior was performed using various dielectric properties of 0–3 composites comprised of varying size powder in a polymer matrix. An intrinsic-microdomain perturbation concept was proposed to interpret observed scaling effects of the relaxor dielectric behavior in contrast to normally accepted extrinsic grain boundary models.

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Ono, Satoshi, Yudai Hanaoka, Isao Matsui, Yorinobu Takigawa, Tokuteru Uesugi, and Kenji Higashi. "Influence of Impurities on Mechanical Properties of Electrodeposited Bulk Nanocrystalline Al." Advanced Materials Research 922 (May 2014): 574–79. http://dx.doi.org/10.4028/www.scientific.net/amr.922.574.

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Effect of typical impurities such as Fe, S, and Cl on mechanical properties of Al electrodeposited from a dimethylsulfone bath (DMSO2bath) were studied. Electrodeposition from a DMSO2bath was conducted to produce the bulk specimens with 0.08–0.24 at.% Fe, 0.47–0.84 at.% S, and 0.59–1.06 at.% Cl, varying the purity of aluminum chloride and current density. Decreasing the current density increased S contents and Cl contents, while the purity of aluminum chloride had no effect on chemical composition of the electrodeposits. The grain sizes were approximately 40–70 nm for Al electrodeposited from a DMSO2bath. The grain sizes decreased with increase in S contents and Cl contents. The electrodeposited bulk nanocrystalline Al exhibited hardness values of 1.56–1.92 GPa. These values were higher than predicted values based on Hall–Petch equation of pure Al. Lattice parameter of samples was less than pure Al. According to Vegard’s law, Fe solute decreases the lattice parameter of Al. These results indicated that the hardness of the electrodeposited bulk nanocrystalline Al was affected by the reduction in the grain size and solid solution strengthening from the Fe contaminant.

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Li, Jian Ping, Ping Wang, Yong Chun Guo, George E. Thompson, Xiao Rong Zhou, Sheirley Zhong, and Teruo Hashimoto. "Microstructure and Microgalvanic Corrosion of an Extruded Mg-10Gd-2Y-0.5Zr Magnesium Alloy." Materials Science Forum 765 (July 2013): 683–87. http://dx.doi.org/10.4028/www.scientific.net/msf.765.683.

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In the present study, the microstructure and corrosion behaviour of an extruded Mg-10Gd-2Y-0.5Zr alloy (noted as GW102) in 3.5 wt.% NaCl for different times have been investigated using a combination of computed phase diagrams, optical microscopy, high resolution scanning electron microscopy (SEM) and scanning Kelvin probe force microscopy (SKPFM). It was revealed that the extruded alloy is composed of fine recrystallized, equiaxed Mg solid solution grains. Additionally different second phases of varying sizes and shapes are present, including a large square-shaped Mg5(Gd,Y) particles which solidified from the melt and are located within the Mg grains and/or at grain boundaries, fine spherical zirconium-rich particles which are located in the Mg grains and fine needle-like precipitates of Mg5(Gd,Y) and Mg24(Gd,Y)5which are uniformly distributed within the Mg grain interior. The latter was formed during thermal extrusion processing. Further, a number of deformation bands or twins were found existing in the magnesium grains. SKPFM potential maps showed that Zr-rich particles and Gd(Y)-rich particles have positive potentials relative to the Mg matrix and the highest potential was recorded on Zr-rich particles. Immersion testing revealed that microgalvanic corrosion initiated at the periphery of Zr-rich particles due to their strong cathodic activity, thereby forming microgalvanic couples with the adjacent Mg grains.

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Shekhar, Shashank, S. Abolghashem, S. Basu, J. Cai, and M. Ravi Shankar. "Interactive Effects of Strain, Strain-Rate and Temperatures on Microstructure Evolution in High Rate Severe Plastic Deformation." Materials Science Forum 702-703 (December 2011): 139–42. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.139.

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During high rate severe plastic deformation (HRSPD), strain and strain-rate are not the only external factors that determine microstructural transformations in materials, temperature-rise due to heat generation from deformation processes, also plays an important role. Temperature may influence the microstructure directly by controlling grain growth kinetics and it may also have an indirect effect through the interactive effect on material behavior, which in turn, influences strain and strain-rate parameters. This complex thermomechanics of HRSPD can lead to myriad of microstructure and consequently, material properties and phenomenon. These deformation parameters can be utilized as a ‘fingerprint’ for the resulting microstructure, and the properties and phenomenon related to it. Here, we capture some of these microstructural transformations by relating grain and sub-grain sizes, to the deformation parameters. In doing so, we find evidence of continuous dynamic recrystallization operative under these HRSPD conditions, where the interplay of strain, strain rate and temperatures offer varying degrees of multimodality in the grain-size distributions.

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Mohamed, Masturah, Mahesh Talari, Mohd Salleh Mohd Deni, and Azlan Zakaria. "Effect of Sintering Temperature on Dielectric Properties of CaCu₃Ti₄O₁₂Ceramics Prepared by Mechanochemical Process." Advanced Materials Research 974 (June 2014): 157–61. http://dx.doi.org/10.4028/www.scientific.net/amr.974.157.

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CaCu3Ti4O12(CCTO) is well known to have colossal dielectric constant in the range of 105.It is widely accepted that this phenomenon may be attributed to internal layer barrier capacitance (IBLC) model. The dielectric properties of CCTO were reported to be strongly dependent on the processing conditions and grain size. In this work, CCTO samples with different grain sizes were produced by varying sintering temperature in order to investigate IBLC effect on dielectric properties of CCTO. The samples were sintered at four different temperatures, (T=1100°C, 1050°C, 1000°C and 950°C). Dielectric measurements were carried out for the samples in the frequency range of 102– 106Hz using impedance spectrometer. Electron micrographs showed that increasing temperature promoted the grain growth of CCTO while sintering. The internal crystalline defects are seen to play major role by increasing the grain conductivity in dipole formation and increased the dielectric constant of the samples.

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Yuan, Huiyu, Minh Nguyen, Tom Hammer, Gertjan Koster, Guus Rijnders, and Johan E. ten Elshof. "Synthesis of KCa2Nb3O10 Crystals with Varying Grain Sizes and Their Nanosheet Monolayer Films As Seed Layers for PiezoMEMS Applications." ACS Applied Materials & Interfaces 7, no. 49 (December 2, 2015): 27473–78. http://dx.doi.org/10.1021/acsami.5b09456.

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Michaelson, Sh, O. Ternyak, R. Akhvlediani, O. A. Williams, D. Gruen, and A. Hoffman. "Hydrogen concentration and bonding in nano-diamond films of varying grain sizes grown by different chemical vapor deposition methods." physica status solidi (a) 204, no. 9 (September 2007): 2860–67. http://dx.doi.org/10.1002/pssa.200776302.

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Bembalge, O. B., and S. K. Panigrahi. "Thermal Stability, Grain Growth Kinetics, and Mechanical Properties of Bulk Ultrafine-Grained AA6063/SiC Composites with Varying Reinforcement Sizes." Metallurgical and Materials Transactions A 50, no. 9 (July 2, 2019): 4288–306. http://dx.doi.org/10.1007/s11661-019-05342-6.

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Lim, Kean Pah, Kuen Hou Cheong, Abdul Halim Shaari, Mansor Hashim, Albert Han Ming Gan, Hui Wei Chin, and Siau Wei Ng. "Influence of Molar Ratio of Citric Acid to Metal Ions on Structure, Microstructure and Electrical Transport Properties on Nanosized La_0.85Na_0.15MnO₃." Advanced Materials Research 1107 (June 2015): 261–66. http://dx.doi.org/10.4028/www.scientific.net/amr.1107.261.

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In this paper, nanosized La0.85Na0.15MnO3 (LNMO) has been synthesized via sol-gel method by involving two major steps, first the complexation of citric acid (CA) with metal ions (MI) and second the polyesterification between CA and ethylene glycol (EG). The effect of molar ratio CA:MI varying from 2-4 on structure, microstructure and electrical transport properties of LNMO have been investigated by constant the amount of EG. All samples show single perovskite phase with hexagonal structure and space group R3c after sintering at 800°C for 10h. Sample of molar ratio 2.5 is observed to possess smallest grain sizes which yield high resistivity value compared with others, is suggested to originate from the increase of tunneling barriers (grain boundaries). The large low field magnetoresistance (LFMR) of about ~ -16% at 0.1T and low temperature confirmed the important role of grain boundaries in the nanosized LNMO.

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Yan, Y., W. M. Stobbs, D. A. Cardwell, and A. M. Campbell. "TEM study of melt-processed “123” YBaCuO containing excess “211”." Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 794–95. http://dx.doi.org/10.1017/s0424820100171705.

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High Jc values of 104~106 A cm-2 are generally required in the use of YBCO. In this context the commonly used sintering method for making bulk high-Tc superconductors has the disadvantage that grain boundaries in such material tend to act as weak links. Melt processesing of the YBaCuO “123” phase has been found to be effective in reducing the problem. In order to understand the mechanisms involved, the physical properties (Tc, Jc, etc.) of YBa2Cu3O7-x (“123”), with varying additions of Y2BaCuO5 (“211”), are being compared and correlated with associated changes in the structure.TEM analysis indicates that the melt processed material contains well aligned tabular “123” platelets with near to common c axis orientations (the preferred orientation for grain growth is in the a-b plane), trapping more equiaxed “211” phase particles of varying sizes. Electron diffraction (Fig.la inset) has shown that there are no large orientation changes between platelets throughout the whole specimen despite their being interconnected by “gaps” where there are phase changes.

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Marcondes Guimarães, Rafael Paiotti, Juliano Soyama, Thomas Ebel, Márcio C. Fredel, and Florian Pyczak. "Influence of α-Phase Field Heat Treatment on the Tensile and Primary Creep Resistance of a Powder Metallurgical Processed Ti-45Al-5Nb-0.2B-0.2C Titanium Aluminide Alloy." Materials Science Forum 899 (July 2017): 418–23. http://dx.doi.org/10.4028/www.scientific.net/msf.899.418.

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In powder metallurgical processing the sintering process, as well as heat treatments, can drastically influence microstructure formation. In the case of γ-titanium aluminides, it is critical to achieve certain microstructure parameters, such as colony size, porosity and grain boundary morphology in order to obtain appropriate mechanical properties. In this study, the effect of a heat treatment implemented after sintering with the objective of varying the colony size was investigated. Specimens of Ti-45Al-5Nb-0.2B-0.2C prepared by metal injection moulding and uniaxial pressing of feedstock were used to evaluate the tensile and creep properties. Heat treatments conducted at 1350 and 1400 °C for 3 h led to colony sizes of approximately 100 and 200 μm, respectively. Classically, there is an inverse relationship between grain size and creep resistance, nonetheless, for γ-titanium aluminides, the morphology of the colony boundaries was also found to play a role. The larger colony sizes achieved with the heat treatments did not improve the primary creep resistance, which was explained by the change in the morphology of the colony boundaries as they became larger.

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SHUAIB-BABATA, YUSUF LANRE, Ibrahim Owolabi Ambali, Lawal Babatunde Abdulqadir, Hassan Kobe Ibrahim, Ishaq Na’allah Aremu, and Taofeek Olawale Ibraheem. "Production of Abrasive Sandpaper using Periwinkle Shells and Crab Shells." International Journal of Engineering Materials and Manufacture 5, no. 2 (June 25, 2020): 55–61. http://dx.doi.org/10.26776/ijemm.05.02.2020.04.

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In this study, the abrasive properties of periwinkle shell and crab shell grains with the binding effect of polyester resin at high concentration were evaluated. The abrasive properties considered were the hardness, compressive strength and wear resistance. The shells were processed into grit standards by crushing, grinding and then sieving using ASTM E11 set of sieves into grain sizes of P40 and P60. Furthermore on, the grits were developed into polymer matrix composite with particles varying from 96 wt.% to 92 wt.% and resin 3 wt.% to 7 wt.% with 1 wt.% each of cobalt naphthalene and methyl ethyl ketone peroxide hardener respectively by mixing and mold compression using a hydraulic press. It was found that, with an increase in polyester resin content, the hardness and compressive strength increased, while the wear rate decreased. The composition with most improved abrasive properties was 92 wt.% periwinkle shell grains to 7 wt.% polyester resin.

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Murmu, Peter P., John Kennedy, Ben J. Ruck, and Andreas Markwitz. "Characterization of the Structural and Electrical Properties of Ion Beam Sputtered ZnO Films." Materials Science Forum 700 (September 2011): 49–52. http://dx.doi.org/10.4028/www.scientific.net/msf.700.49.

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We report the structural and electrical properties of ion beam sputtered ZnO films vacuum annealed at varying temperatures. XRD results revealed that the films grow along thec-axis. The crystallite sizes increase from ~8 to ~30 nm upon annealing at 800ºC. Annealing aided to recover the compressive strain and regain the standard lattice parameter values. The RMS surface roughness increased to ~5.0 nm after annealing at 800ºC as observed in AFM micrographs. Increased resistivity on the annealed films suggested that the oxygen vacancies are compensated by de-trapped oxygen at grain boundaries.

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Pauly, Tyler, and Robin T. Garrod. "Modeling CO, CO2and H2O Ice Abundances in the Envelopes of Young Stellar Objects in the Magellanic Clouds." Proceedings of the International Astronomical Union 13, S332 (March 2017): 47–53. http://dx.doi.org/10.1017/s1743921317006858.

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AbstractMassive young stellar objects (MYSOs) in the Magellanic Clouds (MCs) show infrared absorption features corresponding to significant abundances of CO, CO2and H2O ice along the line of sight, with the relative abundances of these ices varying between sources in the Magellanic Clouds and the Milky Way. We use our gas-grain chemical code MAGICKAL, with multiple grain sizes and grain temperatures, and further expand it with a treatment for increased interstellar radiation field intensity to model the elevated dust temperatures observed in the MCs. We also adjust the elemental abundances used in the chemical models, guided by observations of HII regions in these metal-poor satellite galaxies. With a grid of models, we are able to reproduce the relative ice fractions observed in MC MYSOs, indicating that metal depletion and elevated grain temperature are important drivers of the MYSO envelope ice composition. The observed shortfall in CO in the Small Magellanic Cloud can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances.

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Guzanová, A., J. Brezinová, D. Draganovská, and P. O. Maruschak. "Properties of coatings created by HVOF technology using micro-and nano-sized powder." Koroze a ochrana materialu 63, no. 2 (June 1, 2019): 86–93. http://dx.doi.org/10.2478/kom-2019-0011.

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Abstract The paper focuses on assessment the resistance of hot-sprayed coatings applied by HVOF technology (WC–Co–Cr created using powder of two different grain sizes) against erosive wear by dry-pot wear test in a pin mill at two sample angles. As these coatings are designated for the environment with varying elevated temperatures and often are in contact with the abrasive, the coatings have been subjected to thermal cyclic loading and their erosive resistance has been determined in as-sprayed condition and after the 5th and 10th thermal cycles. The corrosion resistance of coatings was evaluated by linear polarization (Tafel analysis).

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Haque, Farjana, Ravindra Naik Bukke, and Mallory Mativenga. "Reduction of Hysteresis in Hybrid Perovskite Transistors by Solvent-Controlled Growth." Materials 14, no. 10 (May 15, 2021): 2573. http://dx.doi.org/10.3390/ma14102573.

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The effect of crystallization process speed on the morphology of solution-processed methyl ammonium lead iodide (MAPbI3) thin films is investigated. Crystallization speed is controlled by varying the number of annealing steps, temperature, and resting time between steps. The resting period allows solvent-controlled growth (SCG) in which crystallization progresses slowly via an intermediate phase—during which solvents slowly evaporate away from the films. SCG results in fewer residues, fewer pinholes, and larger grain sizes. Consequently, thin-film transistors with SCG MAPbI3 exhibit smaller hysteresis in their current-voltage characteristics than those without, demonstrating the benefits of SCG toward hysteresis-free perovskite devices.

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Lin, Su-Shia, and Jow-Lay Huang. "Improved crystallinity and optical properties of AlOx thin films by a ZnO interlayer." Journal of Materials Research 18, no. 4 (April 2003): 965–72. http://dx.doi.org/10.1557/jmr.2003.0132.

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To ascertain how the substrate influences the quality of AlOx films, AlOx films were grown on a bare glass and a ZnO-deposited glass in this study. By applying a ZnO interlayer before the AlOx deposition, AlOx films exhibited polycrystalline structure rather than amorphous as obtained by sputtering on a bare glass. For AlOx film on the ZnO-deposited glass, the transmission electron microscopy observation showed the coexistence of amorphous and polycrystalline structure, which reveals that the (122) plane in AlOx film is parallel to the surface of the substrate. The grains of the AlOx film grown on a ZnO-deposited glass comprising many small crystallites aggregated with sizes varying between 38 and 54 nm with irregular grain shapes. Besides, the ZnO interlayer with different deposition parameters had a significant effect in the diffusion interface between AlOx and ZnO. The ZnO interlayer could improve the optical transmission of AlOx films, especially when ZnO films are prepared with a high power of 200 W. Therefore, the glass/ZnO may be a good alternative substrate for producing high-quality AlOx films by controlling the epitaxial grain growth. The AlOx films grown on ZnO-deposited glasses have very good qualities in terms of crystallinity and optical properties.

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Shokirov, U., S. Turabjanov, Rakhimova, and F. Badriddinova. "KINETICS OFPYRROLE FORM TICS OFPYRROLE FORMATIONFROM A TIONFROM ACETYLENE, AMMONIA AND AMINES." Technical science and innovation 2018, no. 4 (August 2, 2019): 24–29. http://dx.doi.org/10.51346/tstu-01.18.4.-77-0019.

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The research findings of the pyrrole formation from acetylene, ammonia and amines varying catalysts and reaction conditions have been studied in the work. The cadmium catalysts developed by us selectively lead to pyrroleformation using aluminum fluoride as a promoter. The change in the rate of acetylene consumption depending on the weight of the catalyst according to the Boreskov criterion shows that external diffusion does not influence under the conditions of T-573K and P_ (C_2 H_2) = 0.1 atm. The values of the rate of acetylene consumption of at 4, 2, 1, 0.5 mm sizes of catalyst grains with similar conditions, internal diffusion does not influence on the observed rate of acetylene consumption. Calculation on the Thiele modulus shows that the reaction of acetylene consumption does not experience intradiffusion inhibition. The presence of a noticeable amount of macropores in the porous catalyst grain eliminates the appearance of a temperature gradient and causes a high kinetic ability of the reaction

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VITTAYAKORN, W. C., D. BUNJONG, A. RUANGPHANIT, and N. VITTAYAKORN. "EFFECT OF Co3O4 NANOPARTICLE ON THE PROPERTY OF BARIUM TITANATE CERAMIC." Journal of Advanced Dielectrics 01, no. 02 (April 2011): 229–35. http://dx.doi.org/10.1142/s2010135x11000215.

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Effects of the Co3O4 nanoparticle on the phase formation, microstructure and dielectric properties of barium titanate ceramics are investigated in this study. Co3O4 -doped BaTiO3 ceramics were prepared by the conventional mixed oxide method followed by normal sintering in air. Systematic studies of X-ray diffraction (XRD), scanning electron microscopy and dielectric spectroscopy with varying doping levels were performed. The cell parameters, tetragonality and crystallite size of doped ceramics also were calculated from XRD data. Results showed that the single phase of BaTiO3 gave no evidence of unwanted peak forms in any of the samples. Cubic phase occurred after adding Co3O4 at 0.25 mol%. Various grain sizes and shapes were found in this system. Finally, adding Co3O4 in BaTiO3 ceramics resulted in shifting of the Curie point to a lower temperature. The composition, x = 0.25, showed different dielectric behavior, which related to appearance of the cubic phase and fine grain microstructure.

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Masikane, NF, BK Newman, and UM Scharler. "Grandidierella lignorum (Amphipoda: Aoridae) can be used for assessing the toxicity of sediment with varying grain sizes and low organic content." African Journal of Aquatic Science 44, no. 2 (July 19, 2019): 163–70. http://dx.doi.org/10.2989/16085914.2019.1608152.

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Journal articles on the topic 'Varying grain sizes'

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