Grain-boundary engineering applied to grain growth in a high temperature material

International Nuclear Information System (INIS)

Huda, Z.

1993-01-01

Crystallography of grain boundaries are determined for a high temperature material, before and after grain growth processes, so as to study the induction of special properties useful for application in components of a gas-turbine engine. The philosophy of grain-boundary engineering is applied to grain growth in APK-6, a powder formed nickel-base superalloy so as to establish the possible structure/property relationships. The alloy in the as received condition is shown to possess a strong texture and contained coincident site lattices (CSL) boundaries with most boundaries having sigma values in the range of 3 > sigma > 25. A normal grain-growth heat treatment result in a good population of low angle grain boundaries, and drastically reduces the proportion of CSL boundaries. A strong [011] annealing texture is observed after an intermediate grain growth; most grain boundaries, here, tend to be high angle indicating a possibility of possessing special properties. (author)

Advection-diffusion model for normal grain growth and the stagnation of normal grain growth in thin films

International Nuclear Information System (INIS)

Lou, C.

2002-01-01

An advection-diffusion model has been set up to describe normal grain growth. In this model grains are divided into different groups according to their topological classes (number of sides of a grain). Topological transformations are modelled by advective and diffusive flows governed by advective and diffusive coefficients respectively, which are assumed to be proportional to topological classes. The ordinary differential equations governing self-similar time-independent grain size distribution can be derived analytically from continuity equations. It is proved that the time-independent distributions obtained by solving the ordinary differential equations have the same form as the time-dependent distributions obtained by solving the continuity equations. The advection-diffusion model is extended to describe the stagnation of normal grain growth in thin films. Grain boundary grooving prevents grain boundaries from moving, and the correlation between neighbouring grains accelerates the stagnation of normal grain growth. After introducing grain boundary grooving and the correlation between neighbouring grains into the model, the grain size distribution is close to a lognormal distribution, which is usually found in experiments. A vertex computer simulation of normal grain growth has also been carried out to make a cross comparison with the advection-diffusion model. The result from the simulation did not verify the assumption that the advective and diffusive coefficients are proportional to topological classes. Instead, we have observed that topological transformations usually occur on certain topological classes. This suggests that the advection-diffusion model can be improved by making a more realistic assumption on topological transformations. (author)

Nanoscale abnormal grain growth in (001) epitaxial ceria

International Nuclear Information System (INIS)

Solovyov, Vyacheslav F.; Develos-Bagarinao, Katherine; Nykypanchuk, Dmytro

2009-01-01

X-ray reciprocal-space mapping and atomic force microscopy (AFM) are used to study kinetics and mechanisms of lateral grain growth in epitaxial (001) ceria (CeO 2 ) deposited by pulsed laser deposition on (001) yttria-stabilized zirconia (YSZ) and (12 lowbar 10) (r-cut) sapphire. Rate and character of the grain growth during postannealing at 1050 deg. C are found to be strongly dependent on the type of the epitaxial substrate. Films deposited on YSZ exhibit signatures of normal grain growth, which stagnated after the lateral grain size reaches 40 nm, consistent with the grain-boundary pinning by the thermal grooving. In contrast, when r-cut sapphire substrate was used, abnormal (secondary) grain growth is observed. A small population of grains grow to well over 100 nm consuming smaller, 100 nm large (001) terminations and rendering the sample single-crystalline quality. The grain growth is accompanied by reduction in lateral rms strain, resulting in a universal grain size--rms strain dependence. Analysis of the AFM and x-ray diffraction data leads to the conclusion that bimodal initial grain population consisting of grains with very different sizes is responsible for initiation of the abnormal growth in (001) CeO 2 films on r-cut sapphire. Due to different surface chemistry, when a YSZ substrate is used, the initial grain distribution is monomodal, therefore only normal growth is active. We demonstrate that a 2.2 deg. miscut of the sapphire substrate eliminates the large-grain population, thus suppressing abnormal grain growth. It is concluded that utilization of abnormal grain growth is a promising way for synthesis of large (001) ceria terminations.

Sessile oak (Quercus petraea agg. Ehrendorfer 1967) rare ...

African Journals Online (AJOL)

Sessile oak ( Quercus petraea agg. Ehrendorfer 1967) genetic variability in Serbia was estimated applying cpDNA universal primer pairs. Five different haplotypes were detected in the analyzed sample material from populations in Serbia. The areas in West and Southwest Serbia, with all their specificities, represent an ...

CGG repeat length and AGG interruptions as indicators of fragile X-associated diminished ovarian reserve.

Science.gov (United States)

Lekovich, Jovana; Man, Limor; Xu, Kangpu; Canon, Chelsea; Lilienthal, Debra; Stewart, Joshua D; Pereira, Nigel; Rosenwaks, Zev; Gerhardt, Jeannine

2017-12-21

PurposeFragile X premutation (PM) carriers may experience difficulties conceiving a child probably due to fragile X-associated diminished ovarian reserve (FXDOR). We investigated which subgroups of carriers with a PM are at higher risk of FXDOR, and whether the number of AGG interruptions within the repeat sequence further ameliorates the risk.MethodsWe compared markers of ovarian reserve, including anti-Müllerian hormone, antral follicle count, and number of oocytes retrieved between different subgroups of patients with a PM.ResultsWe found that carriers with midrange repeats size (70-90 CGG) demonstrate significantly lower ovarian reserve. Additionally, the number of AGG interruptions directly correlated with parameters of ovarian reserve. Patients with longer uninterrupted CGG repeats post-AGG interruptions had the lowest ovarian reserve.ConclusionThis study connects AGG interruptions and certain CGG repeat length to reduced ovarian reserve in carriers with a PM. A possible explanation for our findings is the proposed gonadotoxicity of the FMR1 transcripts. Reduction of AGG interruptions could increase the likelihood that secondary RNA structures in the FMR1 messenger RNA are formed, which could cause cell dysfunction within the ovaries. These findings may provide women with guidance regarding their fertility potential and accordingly assist with their family planning.GENETICS in MEDICINE advance online publication, 21 December 2017; doi:10.1038/gim.2017.220.

Grain-growth law during Stage 1 sintering of materials

International Nuclear Information System (INIS)

He Zeming; Ma, J.

2002-01-01

This work investigates the grain-growth behaviour of powder compact during Stage 1 sintering (<90{%} theoretical density). It is widely accepted that grain size is an important state variable in the constitutive modelling in material sintering. However, it is noted that all the existing grain-growth laws proposed in the literature do not incorporate the effect of externally applied stress independently. In this work, a grain-growth law with externally applied stress as a variable was proposed. Alumina powders were forge-sintered at different applied stresses to examine the proposed grain-growth relationship. The proposed grain-growth law was then applied to model the grain-growth process on the sinter forging of tool steel. It is shown that the present proposed grain-growth law provides a good description on the experimental results. (author)

Monte Carlo simulation of grain growth

Directory of Open Access Journals (Sweden)

Paulo Blikstein

1999-07-01

Full Text Available Understanding and predicting grain growth in Metallurgy is meaningful. Monte Carlo methods have been used in computer simulations in many different fields of knowledge. Grain growth simulation using this method is especially attractive as the statistical behavior of the atoms is properly reproduced; microstructural evolution depends only on the real topology of the grains and not on any kind of geometric simplification. Computer simulation has the advantage of allowing the user to visualize graphically the procedures, even dynamically and in three dimensions. Single-phase alloy grain growth simulation was carried out by calculating the free energy of each atom in the lattice (with its present crystallographic orientation and comparing this value to another one calculated with a different random orientation. When the resulting free energy is lower or equal to the initial value, the new orientation replaces the former. The measure of time is the Monte Carlo Step (MCS, which involves a series of trials throughout the lattice. A very close relationship between experimental and theoretical values for the grain growth exponent (n was observed.

Randomly grain growth in metallic materials

Energy Technology Data Exchange (ETDEWEB)

Ramirez, A. [Instituto Politecnico Nacional, (SEPI-ESIME), Unidad Profesional Ticoman, Av. Ticoman 600, Del. G.A.M., C.P. 07340 Distrito Federal, Mexico (Mexico); Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico)], E-mail: adaramil@yahoo.com.mx; Chavez, F. [Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico); Demedices, L. [Instituto Politecnico Nacional, (SEPI-ESIME), Unidad Profesional Ticoman, Av. Ticoman 600, Del. G.A.M., C.P. 07340 Distrito Federal, Mexico (Mexico); Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico); Cruz, A.; Macias, M. [Instituto Politecnico Nacional, (SEPI-ESIQIE), Unidad Profesional Zacatenco, Edif. 6 y Edif. Z planta baja C.P.07300, Distrito Federal, Mexico (Mexico)

2009-10-30

Computational modeling of grain structures is a very important topic in materials science. In this work, the development of the computational algorithms for a mathematical model to predict grain nucleation and grain growth is presented. The model place a number of nucleated points randomly in a liquid pool according with the solid and liquid fractions (X{sub sol} and X{sub liq}) of metal solute and the local temperature distribution (SS{sub I,J}). Then these points grows isotropically until obtain a grain structure with straight interfaces. Different grain morphologies such as columnar and equiaxed can be obtained as a function of the temperature distributions and growth directions.

Randomly grain growth in metallic materials

International Nuclear Information System (INIS)

Ramirez, A.; Chavez, F.; Demedices, L.; Cruz, A.; Macias, M.

2009-01-01

Computational modeling of grain structures is a very important topic in materials science. In this work, the development of the computational algorithms for a mathematical model to predict grain nucleation and grain growth is presented. The model place a number of nucleated points randomly in a liquid pool according with the solid and liquid fractions (X sol and X liq ) of metal solute and the local temperature distribution (SS I,J ). Then these points grows isotropically until obtain a grain structure with straight interfaces. Different grain morphologies such as columnar and equiaxed can be obtained as a function of the temperature distributions and growth directions.

Grain growth in UO2

International Nuclear Information System (INIS)

Hastings, I.J.; Scoberg, J.A.; Walden, W.

1979-06-01

Grain growth studies have been carried out on UO 2 to provide data for the fuel modelling program and to evaluate fuel fabricated in commissioning the Mixed Oxide Fuel Fabrication Laboratory at Chalk River Nuclear Laboratories. Fuel examined includes natural UO 2 commercially fabricated from ADU powder for CANDU reactors; natural UO 2 commercially fabricated from AU powder; natural UO 2 from ADU and AU powder, fabricated in the MOFFL; and commercially fabricated UO 2 enriched 1.7, 4.5, and 9.6 wt. percent U-235 in U. Samples were step-annealed in vacuo at 1870-2070 K for up to 32.5 h. All data fit a (grain size)sup(2.5) versus annealing time relationship. Apparent activation energy for grain growth, Q, depends on fuel type and varies from 150+-10 kJ/mol for early AU powder to 360+-10 kJ/mol for pellets from ADU fabricated in the MOFFL. Grain sizes calculated using the laboratory equation in a fuel performance code tend to be greater than those measured in irradiated natural fuel, suggesting irradiation-induced inhibition of grain growth. However, any inhibition is equivalent to that expected for a systematic 5 percent underpredicition in reactor power. (author)

Stochastic theory of grain growth

International Nuclear Information System (INIS)

Hu Haiyun; Xing Xiusan.

1990-11-01

The purpose of this note is to set up a stochastic theory of grain growth and to derive the statistical distribution function and the average value of the grain radius so as to match them with the experiment further. 8 refs, 1 fig

Phase field simulation of grain growth in porous uranium dioxide

International Nuclear Information System (INIS)

Ahmed, Karim; Pakarinen, Janne; Allen, Todd; El-Azab, Anter

2014-01-01

Graphical abstract: Display Omitted -- Abstract: A novel phase field model has been developed to investigate grain growth in porous polycrystalline UO 2 . Based on a system of Cahn–Hilliard and Allen–Cahn equations, the model takes into consideration both the curvature driven grain boundary motion and pore migration by surface diffusion. As such, the model accounts for the interaction between pore and grain boundary kinetics, which tends to retard the growth process. The phase field model parameters are found in terms of measurable material properties. Hence, quantitative results that can be compared with experiments were obtained. The model has been used to investigate the effect of porosity on the kinetics of grain growth in UO 2 . It is found that, as the amount of porosity increases, grain growth in UO 2 gradually changes from boundary controlled growth to pore controlled growth. For high porosity levels, the grain growth completely stops after a short evolution time. It is also found that the inhomogeneous distribution of pores leads to abnormal grain growth even without taking into account the anisotropy in grain boundary energy and mobility. The effects of porosity, temperature and initial microstructure on grain growth were thoroughly investigated. The model predictions are in good agreement with published experimental results of grain growth in UO 2

Grain Growth in Nanocrystalline Mg-Al Thin Films

Energy Technology Data Exchange (ETDEWEB)

Kruska, Karen; Rohatgi, Aashish; Vemuri, Venkata Rama Ses; Kovarik, Libor; Moser, Trevor H.; Evans, James E.; Browning, Nigel D.

2017-10-05

An improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg - Al thin films containing ~10 wt.% Al and with 14.5 nm average grain size were produced by magnetron-sputtering and subjected to heat-treatments. The grain growth evolution in the early stages of heat treatment at 423 K (150 °C), 473 K (200 °C) and 573K (300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull. The grain growth exponent was found to be 7±2 and the activation energy for grain growth was 31.1±13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. The low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems.

Effects of grain size distribution on the interstellar dust mass growth

OpenAIRE

Hirashita, Hiroyuki; Kuo, Tzu-Ming

2011-01-01

Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitive to grain size di...

Constitutive modeling of stress-driven grain growth in nanocrystalline metals

KAUST Repository

Gürses, Ercan

2013-02-08

In this work, we present a variational multiscale model for grain growth in face-centered cubic nanocrystalline (nc) metals. In particular, grain-growth-induced stress softening and the resulting relaxation phenomena are addressed. The behavior of the polycrystal is described by a conventional Taylor-type averaging scheme in which the grains are treated as two-phase composites consisting of a grain interior phase and a grain boundary-affected zone. Furthermore, a grain-growth law that captures the experimentally observed characteristics of the grain coarsening phenomena is proposed. To this end, the grain size is not taken as constant and varies according to the proposed stress-driven growth law. Several parametric studies are conducted to emphasize the influence of the grain-growth rule on the overall macroscopic response. Finally, the model is shown to provide a good description of the experimentally observed grain-growth-induced relaxation in nc-copper. © 2013 IOP Publishing Ltd.

Methods of assessing grain-size distribution during grain growth

DEFF Research Database (Denmark)

Tweed, Cherry J.; Hansen, Niels; Ralph, Brian

1985-01-01

This paper considers methods of obtaining grain-size distributions and ways of describing them. In order to collect statistically useful amounts of data, an automatic image analyzer is used, and the resulting data are subjected to a series of tests that evaluate the differences between two related...... distributions (before and after grain growth). The distributions are measured from two-dimensional sections, and both the data and the corresponding true three-dimensional grain-size distributions (obtained by stereological analysis) are collected. The techniques described here are illustrated by reference...

A new treatment of transient grain growth

Czech Academy of Sciences Publication Activity Database

Svoboda, Jiří; Fratzl, P.; Zickler, G. A.; Fischer, F. D.

2016-01-01

Roč. 115, AUG (2016), s. 442-447 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA15-06390S Institutional support: RVO:68081723 Keywords : Grain size distribution * Grain growth * Growth kinetics * Thermodynamic modelling * Numerical solution of integro-differential equations Subject RIV: BJ - Thermodynamic s Impact factor: 5.301, year: 2016

Abnormal Grain Growth Suppression in Aluminum Alloys

Science.gov (United States)

Hales, Stephen J. (Inventor); Claytor, Harold Dale (Inventor); Alexa, Joel A. (Inventor)

2015-01-01

The present invention provides a process for suppressing abnormal grain growth in friction stir welded aluminum alloys by inserting an intermediate annealing treatment ("IAT") after the welding step on the article. The IAT may be followed by a solution heat treatment (SHT) on the article under effectively high solution heat treatment conditions. In at least some embodiments, a deformation step is conducted on the article under effective spin-forming deformation conditions or under effective superplastic deformation conditions. The invention further provides a welded article having suppressed abnormal grain growth, prepared by the process above. Preferably the article is characterized with greater than about 90% reduction in area fraction abnormal grain growth in any friction-stir-welded nugget.

Stress-assisted grain growth in nanocrystalline metals: Grain boundary mediated mechanisms and stabilization through alloying

International Nuclear Information System (INIS)

Zhang, Yang; Tucker, Garritt J.; Trelewicz, Jason R.

2017-01-01

The mechanisms of stress-assisted grain growth are explored using molecular dynamics simulations of nanoindentation in nanocrystalline Ni and Ni-1 at.% P as a function of grain size and deformation temperature. Grain coalescence is primarily confined to the high stress region beneath the simulated indentation zone in nanocrystalline Ni with a grain size of 3 nm. Grain orientation and atomic displacement vector mapping demonstrates that coalescence transpires through grain rotation and grain boundary migration, which are manifested in the grain interior and grain boundary components of the average microrotation. A doubling of the grain size to 6 nm and addition of 1 at.% P eliminates stress-assisted grain growth in Ni. In the absence of grain coalescence, deformation is accommodated by grain boundary-mediated dislocation plasticity and thermally activated in pure nanocrystalline Ni. By adding solute to the grain boundaries, the temperature-dependent deformation behavior observed in both the lattice and grain boundaries inverts, indicating that the individual processes of dislocation and grain boundary plasticity will exhibit different activity based on boundary chemistry and deformation temperature.

Kinetics of Grain Growth in 718 Ni-Base Superalloy

Directory of Open Access Journals (Sweden)

Huda Z.

2014-10-01

Full Text Available The Haynes® 718 Ni-base superalloy has been investigated by use of modern material characterization, metallographic and heat treatment equipment. Grain growth annealing experiments at temperatures in the range of 1050 – 1200 oC (1323–1473K for time durations in the range of 20 min-22h have been conducted. The kinetic equations and an Arrhenius-type equation have been applied to compute the grain-growth exponent n and the activation energy for grain growth, Qg, for the investigated alloy. The grain growth exponent, n, was computed to be in the range of 0.066-0.206; and the n values have been critically discussed in relation to the literature. The activation energy for grain growth, Qg, for the investigated alloy has been computed to be around 440 kJ/mol; and the Qg data for the investigated alloy has been compared with other metals and alloys and ceramics; and critically analyzed in relation to our results.

Grain growth in ultrafine titanium powders during sintering

International Nuclear Information System (INIS)

Panigrahi, B.B.; Godkhindi, M.M.

2006-01-01

Grain growth behaviour of fine (∼3 μm) and attrition milled nanocrystalline (∼32 nm) titanium powers during sintering have been studied. The activation energies of grain growth (Q g ) in fine titanium were found to be 192.9 and 142.4 kJ/mol at lower and higher temperature ranges, respectively. The nanocrystalline titanium showed very low values of Q g (54.6 kJ/mol) at lower temperatures and it increased to 273.2 kJ/mol at higher temperatures. The constant (n) in nano Ti system was found to have unusually very high values of 6.5-8.2. The grain boundary rotation along with the diffusional processes could be the grain growth mechanism in nanocrystalline and in fine titanium powders

Equi-axed and columnar grain growth in UO2

International Nuclear Information System (INIS)

White, R.J.

1997-01-01

The grain size of UO 2 is an important parameter in the actual performance and the modelling of the performance of reactor fuel elements. Many processes depend critically on the grain size, for example, the degree of initial densification, the evolution rate of stable fission gases, the release rates of radiologically hazardous fission products, the fission gas bubble swelling rates and the fuel creep. Many of these processes are thermally activated and further impact on the fuel thermal behavior thus creating complex feedback processes. In order to model the fuel performance accurately it is necessary to model the evolution of the fuel grain radius. When UO 2 is irradiated, the fission gases xenon and krypton are created from the fissioning uranium nucleus. At high temperatures these gases diffuse rapidly to the grain boundaries where they nucleate immobile lenticular shaped fission gas bubbles. In this paper the Hillert grain growth model is adapted to account for the inhibiting ''Zener'' effects of grain boundary fission gas porosity on grain boundary mobility and hence grain growth. It is shown that normal grain growth ceases at relatively low levels of irradiation. At high burnups, high temperatures and in regions of high temperature gradients, columnar grain growth is often observed, in some cases extending over more than fifty percent of the fuel radius. The model is further extended to account for the de-pinning of grains in the radial direction by the thermal gradient induced force on a fission gas grain boundary bubble. The observed columnar/equi-axed boundary is in fair agreement with the predictions of an evaporation/condensation model. The grain growth model described in this paper requires information concerning the scale of grain boundary porosity, the local fuel temperature and the local temperature gradient. The model is currently used in the Nuclear Electric version of the ENIGMA fuel modelling code. (author). 14 refs, 3 figs, 1 tab

Correlation of thermodynamics and grain growth kinetics in nanocrystalline metals

International Nuclear Information System (INIS)

Song Xiaoyan; Zhang Jiuxing; Li Lingmei; Yang Keyong; Liu Guoquan

2006-01-01

We investigated the correlation of thermodynamics and grain growth kinetics of nanocrystalline metals both theoretically and experimentally. A model was developed to describe the thermodynamic properties of nanograin boundaries, which could give reliable predictions in the destabilization characteristics of nanograin structures and the slowing down of grain growth kinetics at a constant temperature. Both the temperature-varying and isothermal nanograin growth behaviors in pure nanocrystalline Co were studied to verify the thermodynamic predictions. The experimental results showing that discontinuous nanograin growth takes place at a certain temperature and grain growth rate decreases monotonically with time confirm our thermodynamics-based description of nanograin growth characteristics. Therefore, we propose a thermodynamic viewpoint to explain the deviation of grain growth kinetics in nanocrystalline metals from those of polycrystalline materials

Monte carlo simulation of anisotropic grain growth in liquid phase sintering

International Nuclear Information System (INIS)

Han, Yoon Soo; Kim, Do Kyung

2003-01-01

One of the key techniques in modern engineering ceramic system is microstructural control of anisotropic grain growth because grain orientation and shape proved to have an influence on mechanic, dielectric and electric behavior of ceramics. But until now, computer simulation for grain growth has not sufficiently addressed to this subject. The reason is that simulation algorithm was laborious because it has to contain mass transfer through liquid phase and especially anisotropic grain growth has to be considered based on interfacial properties in real system. The goal of present study is simulation of anisotropic grain growth in liquid phase by Q-states model. To give anisotropic inherency to grains, constraint on mobility to specific boundaries was applied. For comparison, we measured grain size distribution and deduced grain growth kinetics from relation ship between average grain size and time. As a result, the grain size distribution functions become broader and the peak height decreases as the anisotropy is increased. The growth exponent 0.67 and 0.47 found by linear fitting have slightly different values in comparison with work of Grest et al. but similar is trend to the decrease of exponent with anisotropy

Computer-aided analysis of grain growth in metals

DEFF Research Database (Denmark)

Klimanek, P.; May, C.; Richter, H.

1993-01-01

Isothermal grain growth in aluminium, copper and alpha-iron was investigated experimentally at elevated temperatures and quantitatively interpreted by computer simulation on the base of a statistical model described in [4,5,6]. As it is demonstrated for the grain growth kinetics, the experimental...... data can be fitted satisfactorly....

Effect of Time-Dependent Pinning Pressure on Abnormal Grain Growth: Phase Field Simulation

Science.gov (United States)

Kim, Jeong Min; Min, Guensik; Shim, Jae-Hyeok; Lee, Kyung Jong

2018-05-01

The effect of the time-dependent pinning pressure of precipitates on abnormal grain growth has been investigated by multiphase field simulation with a simple precipitation model. The application of constant pinning pressure is problematic because it always induces abnormal grain growth or no grain growth, which is not reasonable considering the real situation. To produce time-dependent pinning pressure, both precipitation kinetics and precipitate coarsening kinetics have been considered with two rates: slow and fast. The results show that abnormal grain growth is suppressed at the slow precipitation rate. At the slow precipitation rate, the overall grain growth caused by the low pinning pressure in the early stage indeed plays a role in preventing abnormal grain growth by reducing the mobility advantage of abnormal grains. In addition, the fast precipitate coarsening rate tends to more quickly transform abnormal grain growth into normal grain growth by inducing the active growth of grains adjacent to the abnormal grains in the early stage. Therefore, the present study demonstrates that the time dependence of the pinning pressure of precipitates is a critical factor that determines the grain growth mode.

Modelling grain growth in the framework of Rational Extended Thermodynamics

International Nuclear Information System (INIS)

Kertsch, Lukas; Helm, Dirk

2016-01-01

Grain growth is a significant phenomenon for the thermomechanical processing of metals. Since the mobility of the grain boundaries is thermally activated and energy stored in the grain boundaries is released during their motion, a mutual interaction with the process conditions occurs. To model such phenomena, a thermodynamic framework for the representation of thermomechanical coupling phenomena in metals including a microstructure description is required. For this purpose, Rational Extended Thermodynamics appears to be a useful tool. We apply an entropy principle to derive a thermodynamically consistent model for grain coarsening due to the growth and shrinkage of individual grains. Despite the rather different approaches applied, we obtain a grain growth model which is similar to existing ones and can be regarded as a thermodynamic extension of that by Hillert (1965) to more general systems. To demonstrate the applicability of the model, we compare our simulation results to grain growth experiments in pure copper by different authors, which we are able to reproduce very accurately. Finally, we study the implications of the energy release due to grain growth on the energy balance. The present unified approach combining a microstructure description and continuum mechanics is ready to be further used to develop more elaborate material models for complex thermo-chemo-mechanical coupling phenomena. (paper)

Modelling grain growth in the framework of Rational Extended Thermodynamics

Science.gov (United States)

Kertsch, Lukas; Helm, Dirk

2016-05-01

Grain growth is a significant phenomenon for the thermomechanical processing of metals. Since the mobility of the grain boundaries is thermally activated and energy stored in the grain boundaries is released during their motion, a mutual interaction with the process conditions occurs. To model such phenomena, a thermodynamic framework for the representation of thermomechanical coupling phenomena in metals including a microstructure description is required. For this purpose, Rational Extended Thermodynamics appears to be a useful tool. We apply an entropy principle to derive a thermodynamically consistent model for grain coarsening due to the growth and shrinkage of individual grains. Despite the rather different approaches applied, we obtain a grain growth model which is similar to existing ones and can be regarded as a thermodynamic extension of that by Hillert (1965) to more general systems. To demonstrate the applicability of the model, we compare our simulation results to grain growth experiments in pure copper by different authors, which we are able to reproduce very accurately. Finally, we study the implications of the energy release due to grain growth on the energy balance. The present unified approach combining a microstructure description and continuum mechanics is ready to be further used to develop more elaborate material models for complex thermo-chemo-mechanical coupling phenomena.

Abnormal grain growth: a non-equilibrium thermodynamic model for multi-grain binary systems

Czech Academy of Sciences Publication Activity Database

Svoboda, Jiří; Fischer, F. D.

2014-01-01

Roč. 22, č. 1 (2014), Art . No. 015013 ISSN 0965-0393 Institutional support: RVO:68081723 Keywords : grain boundary segregation * abnormal grain growth * theory * modelling * solute drag Subject RIV: BJ - Thermodynamics Impact factor: 2.167, year: 2014

Grain growth in thoria and thoria-base fuel pellets (LWBR development program)

Energy Technology Data Exchange (ETDEWEB)

Smid, R.J.

1976-01-01

The kinetics of grain growth in ThO/sub 2/-base sintered compacts were investigated to determine the cause of a nonuniform microstructural cross section. It was concluded that trace impurities which inhibit continuous grain growth at the pellet interior were removed by vaporization at the pellet exterior. This resulted in relatively normal grain growth at the pellet surface and discontinuous grain growth at the pellet interior. Calcining the starting ThO/sub 2/ powder to a slightly higher temperature removed inhibiting impurities but also decreased the driving force for grain growth by reducing the surface area of the powder. Mixing high and low temperature calcined ThO/sub 2/ resulted in improved grain growth. Increased oxygen partial pressure and temperature during sintering increased grain boundary mobility in spite of the inhibiting impurity. The specific inhibiting impurity was not isolated during this investigation.

Shortening of the Lactobacillus paracasei subsp. paracasei BGNJ1-64 AggLb protein switches its activity from auto-aggregation to biofilm formation

Directory of Open Access Journals (Sweden)

Marija Miljković

2016-09-01

Full Text Available AggLb is the largest (318.6 kDa aggregation-promoting protein of Lactobacillus paracasei subsp. paracasei BGNJ1-64 responsible for forming large cell aggregates, which causes auto-aggregation, collagen binding and pathogen exclusion in vitro. It contains an N-terminus leader peptide, followed by six successive collagen binding domains, 20 successive repeats (CnaB-like domains and an LPXTG sorting signal at the C-terminus for cell wall anchoring. Experimental information about the roles of the domains of AggLb is currently unknown. To define the domain that confers cell aggregation and the key domains for interactions of specific affinity between AggLb and components of the extracellular matrix (ECM, we constructed a series of variants of the aggLb gene and expressed them in Lactococcus lactis subsp. lactis BGKP1-20 using a lactococcal promoter. All of the variants contained a leader peptide, an inter collagen binding-CnaB domain region (used to raise an anti-AggLb antibody, an anchor domain and a different number of collagen binding and CnaB-like domains. The role of the collagen binding repeats of the N-terminus in auto-aggregation and binding to collagen and fibronectin was confirmed. Deletion of the collagen binding repeats II, III and IV resulted in a loss of the strong auto-aggregation, collagen and fibronectin binding abilities whereas the biofilm formation capability was increased. The strong auto-aggregation, collagen and fibronectin binding abilities of AggLb were negatively correlated to biofilm formation.

UO2 Grain Growth: Developing Phase Field Models for Pore Dragging, Solute Dragging and Anisotropic Grain Boundary Energies

International Nuclear Information System (INIS)

Ahmed, K.; Tonks, M.; Zhang, Y.; Biner, B.

2016-01-01

A detailed phase field model for the effect of pore drag on grain growth kinetics was implemented in MARMOT. The model takes into consideration both the curvature-driven grain boundary motion and pore migration by surface diffusion. As such, the model accounts for the interaction between pore and grain boundary kinetics, which tends to retard the grain growth process. Our 2D and 3D simulations demonstrate that the model capture all possible pore-grain boundary interactions proposed in theoretical models. For high enough surface mobility, the pores move along with the migrating boundary as a quasi-rigid-body, albeit hindering its migration rate compared to the pore-free case. For less mobile pores, the migrating boundary can separate from the pores. For the pore-controlled grain growth kinetics, the model predicts a strong dependence of the growth rate on the number of pores, pore size, and surface diffusivity in agreement with theroretical models. An evolution equation for the grain size that includes these parameters was derived and showed to agree well with numerical solution. It shows a smooth transition from boundary-controlled kinetics to pore-controlled kinetics as the surface diffusivity decreases or the number of pores or their size increases. This equation can be utilized in BISON to give accurate estimate for the grain size evolution. This will be accomplished in the near future. The effect of solute drag and anisotropy of grain boundary on grain growth will be investigated in future studies.

Equi-axed and columnar grain growth in UO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

White, R J [Berkely Technology Centre, Nuclear Electric plc, Berkeley (United Kingdom)

1997-08-01

The grain size of UO{sub 2} is an important parameter in the actual performance and the modelling of the performance of reactor fuel elements. Many processes depend critically on the grain size, for example, the degree of initial densification, the evolution rate of stable fission gases, the release rates of radiologically hazardous fission products, the fission gas bubble swelling rates and the fuel creep. Many of these processes are thermally activated and further impact on the fuel thermal behavior thus creating complex feedback processes. In order to model the fuel performance accurately it is necessary to model the evolution of the fuel grain radius. When UO{sub 2} is irradiated, the fission gases xenon and krypton are created from the fissioning uranium nucleus. At high temperatures these gases diffuse rapidly to the grain boundaries where they nucleate immobile lenticular shaped fission gas bubbles. In this paper the Hillert grain growth model is adapted to account for the inhibiting ``Zener`` effects of grain boundary fission gas porosity on grain boundary mobility and hence grain growth. It is shown that normal grain growth ceases at relatively low levels of irradiation. At high burnups, high temperatures and in regions of high temperature gradients, columnar grain growth is often observed, in some cases extending over more than fifty percent of the fuel radius. The model is further extended to account for the de-pinning of grains in the radial direction by the thermal gradient induced force on a fission gas grain boundary bubble. The observed columnar/equi-axed boundary is in fair agreement with the predictions of an evaporation/condensation model. The grain growth model described in this paper requires information concerning the scale of grain boundary porosity, the local fuel temperature and the local temperature gradient. The model is currently used in the Nuclear Electric version of the ENIGMA fuel modelling code. (author). 14 refs, 3 figs, 1 tab.

Influence of initial heating during final high temperature annealing on the offset of primary and secondary recrystallization in Cu-bearing grain oriented electrical steels

Science.gov (United States)

Rodriguez-Calvillo, P.; Leunis, E.; Van De Putte, T.; Jacobs, S.; Zacek, O.; Saikaly, W.

2018-04-01

The industrial production route of Grain Oriented Electrical Steels (GOES) is complex and fine-tuned for each grade. Its metallurgical process requires in all cases the abnormal grain growth (AGG) of the Goss orientation during the final high temperature annealing (HTA). The exact mechanism of AGG is not yet fully understood, but is controlled by the different inhibition systems, namely MnS, AlN and CuxS, their size and distribution, and the initial primary recrystallized grain size. Therefore, among other parameters, the initial heating stage during the HTA is crucial for the proper development of primary and secondary recrystallized microstructures. Cold rolled 0.3 mm Cu-bearing Grain Oriented Electrical Steel has been submitted to interrupted annealing experiments in a lab tubular furnace. Two different annealing cycles were applied:• Constant heating at 30°C/h up to 1000°C. Two step cycle with initial heating at 100°C/h up to 600°C, followed by 18 h soaking at 600°C and then heating at 30°C/h up to 1050°C. The materials are analyzed in terms of their magnetic properties, grain size, texture and precipitates. The characteristic magnetic properties are analyzed for the different extraction temperatures and Cycles. As the annealing was progressing, the coercivity values (Hc 1.7T [A/m]) decreased, showing two abrupt drops, which can be associated to the on-set of primary and secondary recrystallization. The primary recrystallized grain sizes and recrystallized fractions are fitted to a model using a non-isothermal approach. This analysis shows that, although the resulting grain sizes were similar, the kinetics for the two step annealing were faster due to the lower recovery. The on-set of secondary recrystallization was also shifted to higher temperatures in the case of the continuous heating cycle, which might end in different final grain sizes and final magnetic properties. In both samples, nearly all the observed precipitates are Al-Si-Mn nitrides

Influence of initial heating during final high temperature annealing on the offset of primary and secondary recrystallization in Cu-bearing grain oriented electrical steels

Directory of Open Access Journals (Sweden)

P. Rodriguez-Calvillo

2018-04-01

Full Text Available The industrial production route of Grain Oriented Electrical Steels (GOES is complex and fine-tuned for each grade. Its metallurgical process requires in all cases the abnormal grain growth (AGG of the Goss orientation during the final high temperature annealing (HTA. The exact mechanism of AGG is not yet fully understood, but is controlled by the different inhibition systems, namely MnS, AlN and CuxS, their size and distribution, and the initial primary recrystallized grain size. Therefore, among other parameters, the initial heating stage during the HTA is crucial for the proper development of primary and secondary recrystallized microstructures. Cold rolled 0.3 mm Cu-bearing Grain Oriented Electrical Steel has been submitted to interrupted annealing experiments in a lab tubular furnace. Two different annealing cycles were applied:• Constant heating at 30°C/h up to 1000°C. Two step cycle with initial heating at 100°C/h up to 600°C, followed by 18 h soaking at 600°C and then heating at 30°C/h up to 1050°C. The materials are analyzed in terms of their magnetic properties, grain size, texture and precipitates. The characteristic magnetic properties are analyzed for the different extraction temperatures and Cycles. As the annealing was progressing, the coercivity values (Hc 1.7T [A/m] decreased, showing two abrupt drops, which can be associated to the on-set of primary and secondary recrystallization. The primary recrystallized grain sizes and recrystallized fractions are fitted to a model using a non-isothermal approach. This analysis shows that, although the resulting grain sizes were similar, the kinetics for the two step annealing were faster due to the lower recovery. The on-set of secondary recrystallization was also shifted to higher temperatures in the case of the continuous heating cycle, which might end in different final grain sizes and final magnetic properties. In both samples, nearly all the observed precipitates are Al

Giant secondary grain growth in Cu films on sapphire

Directory of Open Access Journals (Sweden)

David L. Miller

2013-08-01

Full Text Available Single crystal metal films on insulating substrates are attractive for microelectronics and other applications, but they are difficult to achieve on macroscopic length scales. The conventional approach to obtaining such films is epitaxial growth at high temperature using slow deposition in ultrahigh vacuum conditions. Here we describe a different approach that is both simpler to implement and produces superior results: sputter deposition at modest temperatures followed by annealing to induce secondary grain growth. We show that polycrystalline as-deposited Cu on α-Al2O3(0001 can be transformed into Cu(111 with centimeter-sized grains. Employing optical microscopy, x-ray diffraction, and electron backscatter diffraction to characterize the films before and after annealing, we find a particular as-deposited grain structure that promotes the growth of giant grains upon annealing. To demonstrate one potential application of such films, we grow graphene by chemical vapor deposition on wafers of annealed Cu and obtain epitaxial graphene grains of 0.2 mm diameter.

Grain growth kinetics for B2O3-doped ZnO ceramics

Directory of Open Access Journals (Sweden)

Yuksel Berat

2015-06-01

Full Text Available Grain growth kinetics in 0.1 to 2 mol % B2O3-added ZnO ceramics was studied by using a simplified phenomenological grain growth kinetics equation Gn = K0 · t · exp(-Q/RT together with the physical properties of sintered samples. The samples, prepared by conventional ceramics processing techniques, were sintered at temperatures between 1050 to 1250 °C for 1, 2, 3, 5 and 10 hours in air. The kinetic grain growth exponent value (n and the activation energy for the grain growth of the 0.1 mol % B2O3-doped ZnO ceramics were found to be 2.8 and 332 kJ/mol, respectively. By increasing B2O3 content to 1 mol %, the grain growth exponent value (n and the activation energy decreased to 2 and 238 kJ/mol, respectively. The XRD study revealed the presence of a second phase, Zn3B2O6 formed when the B2O3 content was > 1 mol %. The formation of Zn3B2O6 phase gave rise to an increase of the grain growth kinetic exponent and the grain growth activation energy. The kinetic grain growth exponent value (n and the activation energy for the grain growth of the 2 mol % B2O3-doped ZnO ceramics were found to be 3 and 307 kJ/mol, respectively. This can be attributed to the second particle drag (pinning mechanism in the liquid phase sintering.

Effects of lower cobalt binder concentrations in sintering of tungsten carbide

International Nuclear Information System (INIS)

Li Tao; Li Qingfa; Fuh, J.Y.H.; Yu, P.C.; Wu, C.C.

2006-01-01

Cemented tungsten carbides have received much attention because of their superior characteristics. Traditional cemented tungsten carbides usually contain 3-30 wt% binder phase. In this paper, WC with low Co concentration less than 3 wt% is studied using traditional powder metallurgy. The binder phase has tremendous effect on sinterability of WC. High sinterability and high hardness can be achieved for the WC (0.7 μm) with 0.5 wt% Co. Abnormal grain growth (AGG) is often observed in sintering WC with small amount of Co. It seems that AGG is affected by the concentration of Co and a range of Co concentrations may exist for the large amount of AGG. To control the grain size, VC is added to inhibit the grain growth of WC. It is observed that the hardness is affected by the amount of addition of VC. Controlling the ratio of C/W less than unity at low Co concentrations will result in the production of W 2 C phase. The hardness of WC-Co is affected by the amount of W 2 C phase in the sample and W 2 C is stable during the normal cooling process

Constitutive modeling of stress-driven grain growth in nanocrystalline metals

KAUST Repository

Gü rses, Ercan; Wafai, Husam; El Sayed, Tamer S.

2013-01-01

the influence of the grain-growth rule on the overall macroscopic response. Finally, the model is shown to provide a good description of the experimentally observed grain-growth-induced relaxation in nc-copper. © 2013 IOP Publishing Ltd.

On the fission gas release from oxide fuels during normal grain growth

International Nuclear Information System (INIS)

Paraschiv, M.C.; Paraschiv, A.; Glodeanu, F.

1997-01-01

A mathematical formalism for calculating the fission gas release from oxide fuels considering an arbitrary distribution of fuel grain size with only zero boundary condition for gas diffusion at the grain boundary is proposed. It has also been proved that it becomes unnecessary to consider the grain volume distribution function for fission products diffusion when the grain boundary gas resolution is considered, if thermodynamic forces on grain boundaries are only time dependent. In order to highlight the effect of the normal grain growth on fission gas release from oxide fuels Hillert's and Lifshitz and Slyozov's theories have been selected. The last one was used to give an adequate treatment of normal grain growth for the diffusion-controlled grain boundary movement in oxide fuels. It has been shown that during the fuel irradiation, the asymptotic form of the grain volume distribution functions given by Hillert and Lifshitz and Slyozov models can be maintained but the grain growth rate constant becomes time dependent itself. Experimental results have been used to correlate the two theoretical models of normal grain growth to the fission gas release from oxide fuels. (orig.)

Evolution of grain boundary character distributions in alloy 825 tubes during high temperature annealing: Is grain boundary engineering achieved through recrystallization or grain growth?

International Nuclear Information System (INIS)

Bai, Qin; Zhao, Qing; Xia, Shuang; Wang, Baoshun; Zhou, Bangxin; Su, Cheng

2017-01-01

Grain boundary engineering (GBE) of nickel-based alloy 825 tubes was carried out with different cold drawing deformations by using a draw-bench on a factory production line and subsequent annealing at various temperatures. The microstructure evolution of alloy 825 during thermal-mechanical processing (TMP) was characterized by means of the electron backscatter diffraction (EBSD) technique to study the TMP effects on the grain boundary network and the evolution of grain boundary character distributions during high temperature annealing. The results showed that the proportion of ∑ 3 n coincidence site lattice (CSL) boundaries of alloy 825 tubes could be increased to > 75% by the TMP of 5% cold drawing and subsequent annealing at 1050 °C for 10 min. The microstructures of the partially recrystallized samples and the fully recrystallized samples suggested that the proportion of low ∑ CSL grain boundaries depended on the annealing time. The frequency of low ∑ CSL grain boundaries increases rapidly with increasing annealing time associating with the formation of large-size highly-twinned grains-cluster microstructure during recrystallization. However, upon further increasing annealing time, the frequency of low ∑ CSL grain boundaries decreased markedly during grain growth. So it is concluded that grain boundary engineering is achieved through recrystallization rather than grain growth. - Highlights: •The grain boundary engineering (GBE) is applicable to 825 tubes. •GBE is achieved through recrystallization rather than grain growth. •The low ∑ CSL grain boundaries in 825 tubes can be increased to > 75%.

Accretion growth of water-ice grains in astrophysically-relevant dusty plasma experiment

Science.gov (United States)

Chai, Kil-Byoung; Marshall, Ryan; Bellan, Paul

2016-10-01

The grain growth process in the Caltech water-ice dusty plasma experiment has been studied using a high-speed camera equipped with a long-distance microscope lens. It is found that (i) the ice grain number density decreases four-fold as the average grain length increases from 20 to 80 um, (ii) the ice grain length has a log-normal distribution rather than a power-law dependence, and (iii) no collisions between ice grains are apparent. The grains have a large negative charge so the agglomeration growth is prevented by their strong mutual repulsion. It is concluded that direct accretion of water molecules is in good agreement with the observed ice grain growth. The volumetric packing factor of the ice grains must be less than 0.25 in order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains; this conclusion is consistent with ice grain images showing a fractal character.

The Pinning by Particles of Low and High Angle Grain Boundaries during Grain Growth

DEFF Research Database (Denmark)

Tweed, C.J.; Ralph, B.; Hansen, Niels

1984-01-01

A study has been made using transmission electron microscopy of the pinning of grain boundaries in aluminium during grain growth by fine dispersions of alumina particles. The boundary parameters have been determined with precision and the pinning effects measured using an approach due to Ashby...

Growth rate of YBCO-Ag superconducting single grains

Science.gov (United States)

Congreve, J. V. J.; Shi, Y. H.; Dennis, A. R.; Durrell, J. H.; Cardwell, D. A.

2017-12-01

The large scale use of (RE)Ba2Cu3O7 bulk superconductors, where RE=Y, Gd, Sm, is, in part, limited by the relatively poor mechanical properties of these inherently brittle ceramic materials. It is reported that alloying of (RE)Ba2Cu3O7 with silver enables a significant improvement in the mechanical strength of bulk, single grain samples without any detrimental effect on their superconducting properties. However, due to the complexity and number of inter-related variables involved in the top seeded melt growth (TSMG) process, the growth of large single grains is difficult and the addition of silver makes it even more difficult to achieve successful growth reliably. The key processing variables in the TSMG process include the times and temperatures of the stages within the heating profile, which can be derived from the growth rate during the growth process. To date, the growth rate of the YBa2Cu3O7-Ag system has not been reported in detail and it is this lacuna that we have sought to address. In this work we measure the growth rate of the YBCO-Ag system using a method based on continuous cooling and isothermal holding (CCIH). We have determined the growth rate by measuring the side length of the crystallised region for a number of samples for specified isothermal hold temperatures and periods. This has enabled the growth rate to be modelled and from this an optimized heating profile for the successful growth of YBCO-Ag single grains to be derived.

Dynamic grain growth in superplastic Y-TZP and Al2O3/YTZ

International Nuclear Information System (INIS)

Nieh, T.G.; Tomasello, C.M.; Wadsworth, J.

1990-01-01

This paper reports that both static and dynamic grain growth have been studied during superplastic deformation of fine-grained yttria-stabilized tetragonal zirconia (Y-TZP) and alumina reinforced yttria-stabilized tetragonal zirconia (Al 2 O 3 /YTZ). Grain growth was observed in both materials at temperatures above 1350 degrees C. In the case of Y-TZP, both static and dynamic grain growth were found to obey a similar equation of the form: D 3 -D 0 3 = kt where D is the instantaneous grain size, D 0 is the initial grain size, t is the time, and k is a kinetic constant which depends primarily on temperature and grain boundary energy. The activation energies for Y-TZP were approximately 580 and 520 kJ/mol, for static and dynamic grain growth, respectively. In the case of Al 2 O 3 /YTZ, it was found that the grain growth rate for the Al 2 O 3 phase was slower than that for the ZrO 2 phase. The growth rate of the ZrO 2 phase in Al 2 O 3 /YTZ is, however, similar to that in monolithic ZrO 2 i.e., Y-TZP

Friction-Stir-Welded and Spin-Formed End Domes for Cryogenic Tanks

Science.gov (United States)

Hales, S. J.; Tayon, W. A.; Domack, M. S.

2012-01-01

Manufacturing of single-piece end domes for cryogenic tanks employing spin forming of tailored, friction-stir-welded blanks of Al-Li alloy 2195 plate offers cost and reliability benefits. The introduction of plastic deformation into a friction stir weld is a unique feature of the proposed manufacturing route. This investigation addressed abnormal grain growth [AGG] within the friction stir weldments during postfabrication processing of a prototype dome. The phenomenon of AGG was observed during the solution heat treatment [SHT] phase of T8 tempering and is a major concern for meeting specifications. Such abrupt microstructural transitions can be detrimental to notch-sensitive mechanical properties, such as ductility and/or fracture toughness. If the issue of AGG cannot be resolved, then the acceptance of this approach as a viable manufacturing route may be in jeopardy. The innovative approach adopted in this investigation was the insertion of a stand-alone, Intermediate Annealing Treatment [IAT] between the spin forming and T8 processing operations. A simple, recovery annealing step was deemed to be the most readily-scalable solution when fabricating thin-walled, ellipsoidal domes. The research effort culminated in the development of an effective IAT, which resulted in a significant decrease in AGG following SHT. The processing philosophy adopted in designing the IAT is outlined and the microstructural reasons for success are discussed. The analytical results presented are consistent with promoting continuous grain growth during the IAT, thereby suppressing AGG during the SHT.

Mesoscopic simulation of recrystallization and grain growth

International Nuclear Information System (INIS)

Rollett, A.D.

2000-01-01

A brief summary of simulation techniques for recrystallization and grain growth is given. The available methods include surface evolver, front tracking (including finite element methods and vertex methods), networks of curves, phase field, cellular automata, and Monte Carlo. Two of the models that use a regular lattice, the Potts model and the Cellular Automaton (CA) model, have proved to be very useful. Microstructure is represented on a discrete lattice where the value of the field at each point represents the local orientation of the material and boundaries exist between points of unlike orientation. Two issues are discussed: one is a hybrid approach to combining the standard Monte Carlo and cellular automata algorithms for recrystallization modeling. The second is adaptation of the MC method for modeling grain growth (and recrystallization) with physically based boundary properties. Both models have significant limitations in their standard forms. The CA model is very useful and efficient for simulating recrystallization with deterministic motion of the recrystallization fronts. It can be adapted to simulate curvature driven migration provided that multiple sub-lattices are used with a probabilistic switching rule. The Potts model is very successful in modeling curvature driven boundary migration and grain growth. It does not simulate the proportionality between boundary velocity and a stored energy driving force, however, unless rather restricted conditions of stored energy (in relation to the grain boundary energy) and lattice temperature are satisfied. A new approach based on a hybrid of the Potts model (MC) and the Cellular Automaton (CA) model has been developed to obtain the desired limiting behavior for both curvature-driven and stored energy-driven grain boundary migration. The combination of methods is achieved by interleaving the two different types of reorientation event in time. The results show that the hybrid algorithm models the Gibbs

Growth order and activation energies for grain growth of Ti-6Al-4V alloy in β phase

International Nuclear Information System (INIS)

Gil, F.J.; Planell, J.A.

1991-01-01

This paper reports that one of the reasons usually stated for avoiding annealing treatments and hot working of Ti-6Al-4V alloy at temperatures over the β transus is the large grain growth which takes place at such temperatures. The aim of the present work is to quantify the grain growth kinetics when the alloy is heat treated in its β phase. It is well known that the driving force for grain growth comes from the surface energy of the grain boundaries. When thermal energy is given to the material, diffusion takes place which leads to grain selection. This means that the number of grains decreases, their size increases, the area of the grain boundaries decreases with the total energy stored in them and consequently a state of higher thermodynamic stability is reached

Statistical Theory of Normal Grain Growth Revisited

International Nuclear Information System (INIS)

Gadomski, A.; Luczka, J.

2002-01-01

In this paper, we discuss three physically relevant problems concerning the normal grain growth process. These are: Infinite vs finite size of the system under study (a step towards more realistic modeling); conditions of fine-grained structure formation, with possible applications to thin films and biomembranes, and interesting relations to superplasticity of materials; approach to log-normality, an ubiquitous natural phenomenon, frequently reported in literature. It turns out that all three important points mentioned are possible to be included in a Mulheran-Harding type behavior of evolving grains-containing systems that we have studied previously. (author)

Investigation of grain competitive growth during directional solidification of single-crystal nickel-based superalloys

Energy Technology Data Exchange (ETDEWEB)

Zhao, Xinbao [National Energy R and D Center of Clean and High-Efficiency Fossil-Fired Power Generation Technology, Xi' an Thermal Power Research Institute Co. Ltd., Xi' an (China); Northwestern Polytechnical University, State Key Laboratory of Solidification Processing, Xi' an (China); Liu, Lin; Zhang, Jun [Northwestern Polytechnical University, State Key Laboratory of Solidification Processing, Xi' an (China)

2015-08-15

Grain competitive growth of nickel-based single-crystal superalloys during directional solidification was investigated. A detailed characterization of bi-crystals' competitive growth was performed to explore the competitive grain evolution. It was found that high withdrawal rate improved the efficiency of grain competitive growth. The overgrowth rate was increased when the misorientation increased. Four patterns of grain competitive growth with differently oriented dispositions were characterized. The results indicated that the positive branching of the dendrites played a significant role in the competitive growth process. The effect of crystal orientation and heat flow on the competitive growth can be attributed to the blocking mechanism between the adjacent grains. (orig.)

Strain-induced grain growth of cryomilled nanocrystalline Al in trimodal composites during forging

International Nuclear Information System (INIS)

Yao, B.; Simkin, B.; Majumdar, B.; Smith, C.; Bergh, M. van den; Cho, K.; Sohn, Y.H.

2012-01-01

Highlights: ► Grain growth of cryomilled nanocrystalline aluminum during hot forging. ► Use of hollow cone dark field imaging technique in TEM for grain size measurement. ► Grain growth model of strain, strain rate and temperature for forging optimization. - Abstract: Grain growth of nanocrystalline aluminum ( nc Al) in trimodal Al metal-matrix-composites (MMCs) during hot forging was investigated. The nc Al phase formed through cryomilling of inert gas-atomized powders in liquid nitrogen has an average grain size down to 21 nm, exhibits excellent thermal stability. However, substantial grain growth of nc Al up to 63 nm was observed when the Al MMCs were thermo-mechanically processed even at relatively low temperatures. Grain growth of the cryomilled nc Al phase in trimodal Al MMCs after hot forging was documented with respect to temperature ranging from 175 °C to 287 °C, true strain ranging from 0.4 to 1.35 and strain rate ranging from 0.1 to 0.5 s −1 . Hollow cone dark field imaging technique was employed to provide statistically confident measurements of nc Al grain size that ranged from 21 to 63 nm. An increase in forging temperature and an increase in true strain were correlated with an increase in grain size of nc Al. Results were correlated to devise a phenomenological grain growth model for forging that takes strain, strain rate and temperature into consideration. Activation energy for the grain growth during thermo-mechanical hot-forging was determined to be 35 kJ/mol, approximately a quarter of activation energy for bulk diffusion of Al and a half of activation energy for static recrystallization.

Anisotropic atomic packing model for abnormal grain growth mechanism of WC-25 wt.% Co alloy

International Nuclear Information System (INIS)

Ryoo, H.S.; Hwang, S.K.

1998-01-01

During liquid phase sintering, cemented carbide particles grow into either faceted or non-faceted grain shapes depending on ally system. In case of WC-Co alloy, prism-shape faceted grains with (0001) planes and {1 bar 100} planes on each face are observed, and furthermore an abnormal grain growth has been reported to occur. When abnormal grain growth occurs in WC crystals, dimension ratio, R, of the length of the side of the triangular prism face to the height of the prism is higher than 4 whereas that for normal grains is approximately 2. Abnormal grain growth in this alloy is accelerated by the fineness of starting powders and by high sintering temperature. To account for the mechanism of the abnormal grain growth, there are two proposed models which drew much research attention: nucleation and subsequent carburization and transformation of η (W 3 Co 3 C) phase into WC, and coalescence of coarse WC grains through dissolution and re-precipitation. Park et al. proposed a two-dimensional nucleation theory to explain the abnormal grain growth of faceted grains. There are questions, however, on the role of η phase on abnormal grain growth. The mechanism of coalescence of spherical grains as proposed by Kingery is also unsuitable for faceted grains. So far theories on abnormal grain growth do not provide a satisfactory explanation on the change of R value during the growth process. In the present work a new mechanism of nucleation and growth of faceted WC grains is proposed on the ground of anisotropic packing sequence of each atom

Direct observation of densification and grain growth in a W--Ni alloy

International Nuclear Information System (INIS)

Riegger, H.; Pask, J.A.; Exner, H.E.

1979-04-01

Densification and grain growth in a tungsten--nickel alloy containing 32 vol % of liquid at 1550 0 C were studied by conventional methods aided by hot stage scanning electron microscopy and cinematography. This technique yields important additional qualitative information on the mechanisms. Two stages can be discerned. In stage 1, essentially complete pore elimination, rapid grain growth and adjustment of microstructural geometry take place. In the second stage, microstructure coarsening occurs which is characterized by geometric similarity. Columnar grain growth at the surface is observed due to squeezing out of Ni--W liquid, flooding of surface grains and fast evaporation of the Ni. The driving forces for these processes are discussed showing that a high ratio of grain boundary energy to liquid surface energy is essential. A W--Cu alloy with 32 vol % liquid at 1100 0 C did not show any grain growth due to essentially no solubility of W in Cu at this temperature

The Relationship Between Debris and Grain Growth in Polycrystalline Ice

Science.gov (United States)

Rivera, A.; McCarthy, C.

2017-12-01

An understanding of the mechanisms of ice flow, as well as the factors that affect it, must be improved in order to make more accurate predictions of glacial melting rates, and hence, sea level rise. Both field and laboratory studies have made an association between smaller grain sizes of ice and more rapid deformation. Therefore, it is essential to understand the different factors that affect grain size. Observations from ice cores have shown a correlation between debris content in layers of ice with smaller grain sizes, whereas layers with very little debris have larger grain sizes. Static grain growth rates for both pure ice and ice containing bubbles are well constrained, but the effect of small rock/dust particles has received less attention. We tested the relationship between debris and grain growth in polycrystalline ice with controlled annealing at -5°C and microstructural characterization. Three samples, two containing fine rock powder and one without, were fabricated, annealed, and imaged over time. The samples containing powder had different initial grain sizes due to solidification temperature during fabrication. Microstructural analysis was done on all samples after initial fabrication and at various times during the anneal using a light microscope housed in a cold room. Microstructural images were analyzed by the linear-intercept method. When comparing average grain size over time between pure ice and ice with debris, it was found that the rate of growth for the pure ice was larger than the rate of growth for the ice with debris at both initial grain sizes. These results confirm the observations seen in nature, and suggest that small grain size is indeed influenced by debris content. By understanding this, scientists could gain a more in-depth understanding of internal ice deformation and the mechanisms of ice flow. This, in turn, helps improve the accuracy of glacial melting predictions, and sea level rise in the future.

Growth of preexisting abnormal grains in molybdenum under static and dynamic conditions

Energy Technology Data Exchange (ETDEWEB)

Noell, Philip J. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-0889 (United States); Worthington, Daniel L. [Verily Life Sciences, 269 E. Grand Ave., South San Francisco, CA 94080, USA (United States); Taleff, Eric M., E-mail: taleff@utexas.edu [The University of Texas at Austin, Department of Mechanical Engineering, 204 East Dean Keeton St., Stop C2200, Austin, TX 78712 (United States)

2017-04-24

This investigation compares the growth rates of preexisting abnormal grains under both static and dynamic conditions. Abnormal grains several millimeters in length were produced in two commercial-purity molybdenum (Mo) materials by tensile straining at temperatures from 1923 to 2073 K (1650–1800 °C). This process is termed dynamic abnormal grain growth (DAGG) because it produces abnormal grains during concurrent plastic straining. DAGG creates abnormal grains at much lower temperatures than does static abnormal grain growth (SAGG). Abnormal grains created through DAGG were characterized with their surrounding microstructures and were then subjected to annealing treatments. Only one-third of the preexisting abnormal grains subsequently grew by SAGG. Among these, SAGG occurred only in those specimens that required the largest strains to initiate DAGG when creating the abnormal grain(s). The rates of boundary migration observed for SAGG were approximately two orders of magnitude slower than those for DAGG. When DAGG in one specimen was interrupted by extended static annealing, it did not recur when straining resumed. The dislocation substructure developed during hot deformation, which includes subgrains typical of five-power creep, is critically important to both DAGG and SAGG of preexisting abnormal grains under the conditions examined.

Grain growth kinetics in uranium-plutonium mixed oxides

International Nuclear Information System (INIS)

Sari, C.

1986-01-01

Grain growth rates were investigated in uranium-plutonium mixed oxide specimens with oxygen-to-metal ratios 1.97 and 2.0. The specimens in the form of cylindrical pellets were heated in a temperature gradient similar to that existing in a fast reactor. The results are in agreement with the cubic rate law. The mean grain size D(μm) after annealing for time t (min) is represented by D 3 -D 0 3 =1.11x10 12 . exp(-445870/RT).t and D 3 -D 0 3 =2.55x10 9 .exp(-319240/RT).t for specimens with overall oxygen-to-metal ratios 1.97 and 2.0, respectively (activation energies expressed in J/mol). An example for the influence of the oxygen-to-metal ratio on the grain growth in mixed oxide fuel during operation in a fast reactor is also given. (orig.)

Analysis of controlled-mechanism of grain growth in undercooled Fe-Cu alloy

International Nuclear Information System (INIS)

Chen Zheng; Liu Feng; Yang Xiaoqin; Shen Chengjin; Fan Yu

2011-01-01

Highlights: → In terms of a thermo-kinetic model applicable for micro-scale undercooled Fe-4 at.% Cu alloy, grain growth behavior of the single-phase supersaturated granular grain was investigated. → In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, two characteristic annealing time were determined. → The controlled-mechanism of grain growth in undercooled Fe-Cu alloy was proposed, including a mainly kinetic-controlled process, a transition from kinetic-mechanism to thermodynamic-mechanism and purely thermodynamic-controlled process. - Abstract: An analysis of controlled-mechanism of grain growth in the undercooled Fe-4 at.% Cu immiscible alloy was presented. Grain growth behavior of the single-phase supersaturated granular grains prepared in Fe-Cu immiscible alloy melt was investigated by performing isothermal annealings at 500-800 deg. C. The thermo-kinetic model [Chen et al., Acta Mater. 57 (2009) 1466] applicable for nano-scale materials was extended to the system of micro-scale undercooled Fe-4 at.% Cu alloy. In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, two characteristic annealing time (t 1 and t 2 ) were determined. The controlled-mechanism of grain growth in undercooled Fe-Cu alloy was proposed, including a mainly kinetic-controlled process (t ≤ t 1 ), a transition from kinetic-mechanism to thermodynamic-mechanism (t 1 2 ) and purely thermodynamic-controlled process (t ≥ t 2 ).

Competitive grain growth in directional solidification investigated by phase field simulation

International Nuclear Information System (INIS)

Li Junjie; Wang Zhijun; Wang Jincheng; Yang Yujuan

2012-01-01

During directional solidification, the competitive dendritic growth between various oriented grains is a key factor to obtain desirable texture. In order to understand the mechanism of competitive dendritic growth, the phase field method was adopted to simulate the microstructure evolution of bicrystal samples. The simulation has well reproduced the whole competitive growth process for both diverging and converging dendrites. In converging case, besides the block of the unfavorably oriented dendrite by the favorably oriented one, the unfavorably oriented dendrite is also able to overgrow the favorable one under the condition of relatively low pulling velocity. This unusual overgrowth is dictated by the solute interaction of the converging dendrite tips. In diverging case, it was found that the grain boundary can be either inclined or parallel to the favorably oriented grain depending on the disposition of two grains.

Grain Growth in Samples of Aluminum Containing Alumina Particles

DEFF Research Database (Denmark)

Tweed, C. J.; Hansen, Niels; Ralph, B.

1983-01-01

A study of the two-dimensional and three-dimensional grain size distributions before and after grain growth treatments has been made in samples having a range of oxide contents. In order to collect statistically useful amounts of data, an automatic image analyzer was used and the resulting data w...

Normal and abnormal grain growth in fine-grained Nd-Fe-B sintered magnets prepared from He jet milled powders

Energy Technology Data Exchange (ETDEWEB)

Bittner, F., E-mail: f.bittner@ifw-dresden.de [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany); Technische Universität Dresden, Institute of Materials Science, 01062 Dresden (Germany); Woodcock, T.G. [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany); Schultz, L. [IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden (Germany); Technische Universität Dresden, Institute of Materials Science, 01062 Dresden (Germany); Schwöbel, C. [Technische Universität Darmstadt, Materialwissenschaft, Alarich-Weiß-Str. 16, 64287 Darmstadt (Germany); Gutfleisch, O. [Technische Universität Darmstadt, Materialwissenschaft, Alarich-Weiß-Str. 16, 64287 Darmstadt (Germany); Fraunhofer ISC, Projektgruppe für Werkstoffkreisläufe und Ressourcenstrategie IWKS, Rodenbacher Chaussee 4, 63457 Hanau (Germany); Zickler, G.A.; Fidler, J. [Technische Universität Wien, Institute of Solid State Physics, Wiedner Hauptstr. 8-10, 1040 Wien (Austria); Üstüner, K.; Katter, M. [Vacuumschmelze GmbH & Co. KG, 63412 Hanau (Germany)

2017-03-15

Fine-grained, heavy rare earth free Nd-Fe-B sintered magnets were prepared from He jet milled powders with an average particle size of 1.5 µm by low temperature sintering at 920 °C or 980 °C. A coercivity of >1600 kA/m was achieved for an average grain size of 1.68 µm. Transmission electron microscopy showed that the distribution and composition of intergranular and grain boundary junction phases was similar to that in conventionally processed magnets. Microstructural analysis on different length scales revealed the occurrence of abnormal grain growth, which is unexpected for sintering temperatures below 1000 °C. A larger area fraction of abnormal grains was observed in the sample sintered at 920 °C compared to that sintered at 980 °C. Microtexture investigation showed a better crystallographic alignment of the abnormal grains compared to the fine-grained matrix, which is explained by a size dependent alignment of the powder particles during magnetic field alignment prior to sintering. Slightly larger particles in the initial powder show a better alignment and will act as nucleation sites for abnormal grain growth. Magneto-optical Kerr investigations confirmed the lower switching field of the abnormal grains compared to the fine-grained matrix. The demagnetisation curve of the sample sintered at 920 °C showed reduced rectangularity and this was attributed to a cooperative effect of the larger fraction of abnormal grains with low switching field and, as a minor effect, a reduced degree of crystallographic texture in this sample compared to the material sintered at 980 °C, which did not show the reduced rectangularity of the demagnetisation curve. - Highlights: • He Jet milling to reduce Nd-Fe-B grain size and to enhance coercivity. • Normal and abnormal grain growth observed for low temperature sintering. • Well oriented abnormal grown grains explained by size dependent field alignment. • Poor rectangularity is caused by low nucleation field of

Normal and abnormal grain growth in fine-grained Nd-Fe-B sintered magnets prepared from He jet milled powders

International Nuclear Information System (INIS)

Bittner, F.; Woodcock, T.G.; Schultz, L.; Schwöbel, C.; Gutfleisch, O.; Zickler, G.A.; Fidler, J.; Üstüner, K.; Katter, M.

2017-01-01

Fine-grained, heavy rare earth free Nd-Fe-B sintered magnets were prepared from He jet milled powders with an average particle size of 1.5 µm by low temperature sintering at 920 °C or 980 °C. A coercivity of >1600 kA/m was achieved for an average grain size of 1.68 µm. Transmission electron microscopy showed that the distribution and composition of intergranular and grain boundary junction phases was similar to that in conventionally processed magnets. Microstructural analysis on different length scales revealed the occurrence of abnormal grain growth, which is unexpected for sintering temperatures below 1000 °C. A larger area fraction of abnormal grains was observed in the sample sintered at 920 °C compared to that sintered at 980 °C. Microtexture investigation showed a better crystallographic alignment of the abnormal grains compared to the fine-grained matrix, which is explained by a size dependent alignment of the powder particles during magnetic field alignment prior to sintering. Slightly larger particles in the initial powder show a better alignment and will act as nucleation sites for abnormal grain growth. Magneto-optical Kerr investigations confirmed the lower switching field of the abnormal grains compared to the fine-grained matrix. The demagnetisation curve of the sample sintered at 920 °C showed reduced rectangularity and this was attributed to a cooperative effect of the larger fraction of abnormal grains with low switching field and, as a minor effect, a reduced degree of crystallographic texture in this sample compared to the material sintered at 980 °C, which did not show the reduced rectangularity of the demagnetisation curve. - Highlights: • He Jet milling to reduce Nd-Fe-B grain size and to enhance coercivity. • Normal and abnormal grain growth observed for low temperature sintering. • Well oriented abnormal grown grains explained by size dependent field alignment. • Poor rectangularity is caused by low nucleation field of

Grain growth in uranium nitride prepared by spark plasma sintering

Science.gov (United States)

Johnson, Kyle D.; Lopes, Denise Adorno

2018-05-01

Uranium mononitride (UN) has long been considered a potential high density, high performance fuel candidate for light water reactor (LWR) and fast reactor (FR) applications. However, deployability of this fuel has been limited by the notable resistance to sintering and subsequent difficulty in producing a desirable microstructure, the high costs associated with 15N enrichment, as well as the known proclivity to oxidation and interaction with steam. In this study, the stimulation of grain growth in UN pellets sintered using SPS has been investigated. The results reveal that by using SPS and controlling temperature, time, and holding pressure, grain growth can be stimulated and controlled to produce a material featuring both a desired porosity and grain size, at least within the range of interest for nuclear fuel candidates. Grain sizes up to 31 μm were obtained using temperatures of 1650 °C and hold times of 15 min. Evaluation by EBSD reveal grain rotation and coalescence as the dominant mechanism in grain growth, which is suppressed by the application of higher external pressure. Moreover, complete closure of the porosity of the material was observed at relative densities of 96% TD, resulting in a material with sufficient porosity to accommodate LWR burnup. These results indicate that a method exists for the economic fabrication of an 15N-bearing uranium mononitride fuel with favorable microstructural characteristics compatible with use in a light water-cooled nuclear reactor.

Grain growth of metal uranium; Rast zrna kod metalnog urana

Energy Technology Data Exchange (ETDEWEB)

Cerovic, D [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

1965-11-15

In order to study the grain growth, uranium samples were deformed by molding up to 50% and then by rolling at 600 deg C for recrystallization. Grains obtained by recrystallization having diameter 10 - 15 {mu} were heated at different temperatures and during different time intervals to record the changes of grain size. Characteristic grain growth values, rate constants, time exponent and activation energy, were calculated by using the obtained data. U cilju proucavanja rasta zrna uzorci urana deformisani su valjanjem do 50%, a zatim zareni na 600 deg C da rekristalisu. Rekristalizacijom su dobijena sitna zrna, precnika 10-15 {mu} koja su zatim podvrgavana zarenju pri raznim temperaturama i razlicitm vremenskim intervalima, pri cemu je pracena promena velicine zrna. Na osnovu dobijenih podataka izracunate su karakteristicne velicine rasta zrna: konstante brzine, vremenski eksponent i energija aktivacije (author)

Understanding and Tailoring Grain Growth of Lead-Halide Perovskite for Solar Cell Application.

Science.gov (United States)

Ma, Yongchao; Liu, Yanliang; Shin, Insoo; Hwang, In-Wook; Jung, Yun Kyung; Jeong, Jung Hyun; Park, Sung Heum; Kim, Kwang Ho

2017-10-04

The fundamental mechanism of grain growth evolution in the fabrication process from the precursor phase to the perovskite phase is not fully understood despite its importance in achieving high-quality grains in organic-inorganic hybrid perovskites, which are strongly affected by processing parameters. In this work, we investigate the fundamental conversion mechanism from the precursor phase of perovskite to the complete perovskite phase and how the intermediate phase promotes growth of the perovskite grains during the fabrication process. By monitoring the morphological evolution of the perovskite during the film fabrication process, we observed a clear rod-shaped intermediate phase in the highly crystalline perovskite and investigated the role of the nanorod intermediate phase on the growth of the grains of the perovskite film. Furthermore, on the basis of these findings, we developed a simple and effective method to tailor grain properties including the crystallinity, size, and number of grain boundaries, and then utilized the film with the tailored grains to develop perovskite solar cells.

Comparative Mitogenomics of Plant Bugs (Hemiptera: Miridae): Identifying the AGG Codon Reassignments between Serine and Lysine

Science.gov (United States)

Wang, Pei; Song, Fan; Cai, Wanzhi

2014-01-01

Insect mitochondrial genomes are very important to understand the molecular evolution as well as for phylogenetic and phylogeographic studies of the insects. The Miridae are the largest family of Heteroptera encompassing more than 11,000 described species and of great economic importance. For better understanding the diversity and the evolution of plant bugs, we sequence five new mitochondrial genomes and present the first comparative analysis of nine mitochondrial genomes of mirids available to date. Our result showed that gene content, gene arrangement, base composition and sequences of mitochondrial transcription termination factor were conserved in plant bugs. Intra-genus species shared more conserved genomic characteristics, such as nucleotide and amino acid composition of protein-coding genes, secondary structure and anticodon mutations of tRNAs, and non-coding sequences. Control region possessed several distinct characteristics, including: variable size, abundant tandem repetitions, and intra-genus conservation; and was useful in evolutionary and population genetic studies. The AGG codon reassignments were investigated between serine and lysine in the genera Adelphocoris and other cimicomorphans. Our analysis revealed correlated evolution between reassignments of the AGG codon and specific point mutations at the antidocons of tRNALys and tRNASer(AGN). Phylogenetic analysis indicated that mitochondrial genome sequences were useful in resolving family level relationship of Cimicomorpha. Comparative evolutionary analysis of plant bug mitochondrial genomes allowed the identification of previously neglected coding genes or non-coding regions as potential molecular markers. The finding of the AGG codon reassignments between serine and lysine indicated the parallel evolution of the genetic code in Hemiptera mitochondrial genomes. PMID:24988409

Large scale statistics for computational verification of grain growth simulations with experiments

International Nuclear Information System (INIS)

Demirel, Melik C.; Kuprat, Andrew P.; George, Denise C.; Straub, G.K.; Misra, Amit; Alexander, Kathleen B.; Rollett, Anthony D.

2002-01-01

It is known that by controlling microstructural development, desirable properties of materials can be achieved. The main objective of our research is to understand and control interface dominated material properties, and finally, to verify experimental results with computer simulations. We have previously showed a strong similarity between small-scale grain growth experiments and anisotropic three-dimensional simulations obtained from the Electron Backscattered Diffraction (EBSD) measurements. Using the same technique, we obtained 5170-grain data from an Aluminum-film (120 (micro)m thick) with a columnar grain structure. Experimentally obtained starting microstructure and grain boundary properties are input for the three-dimensional grain growth simulation. In the computational model, minimization of the interface energy is the driving force for the grain boundary motion. The computed evolved microstructure is compared with the final experimental microstructure, after annealing at 550 C. Characterization of the structures and properties of grain boundary networks (GBN) to produce desirable microstructures is one of the fundamental problems in interface science. There is an ongoing research for the development of new experimental and analytical techniques in order to obtain and synthesize information related to GBN. The grain boundary energy and mobility data were characterized by Electron Backscattered Diffraction (EBSD) technique and Atomic Force Microscopy (AFM) observations (i.e., for ceramic MgO and for the metal Al). Grain boundary energies are extracted from triple junction (TJ) geometry considering the local equilibrium condition at TJ's. Relative boundary mobilities were also extracted from TJ's through a statistical/multiscale analysis. Additionally, there are recent theoretical developments of grain boundary evolution in microstructures. In this paper, a new technique for three-dimensional grain growth simulations was used to simulate interface migration

Explosive anisotropic grain growth of delta-NiMo by solid-state diffusion

International Nuclear Information System (INIS)

Chou, T.C.; Nieh, T.G.

1991-01-01

Anomalous, anisotropic grain growth has been observed in delta(δ)-NiMo intermetallic compound during the annealings of Mo/Ni thin-film diffusion couples at 700 and 800 degree C. Two layered microstructures showing median-sized, equiaxed grains and large columnar single crystalline grains were generated. The growth direction of the columnar grains was parallel to the direction of Ni diffusion flux. Electron diffraction indicated that both the median-sized and the columnar grains were δ-NiMo. The composition of δ-NiMo was determined to be Ni48-Mo52 (at.%). According to the thickness of reaction-formed δ-NiMo, the apparent interdiffusion coefficient was measured to be about 10 -10 cm 2 /s which is 4 to 5 orders of magnitude greater than literature data. The enhanced diffusion rate in Ni-Mo, and the anomalous anisotropic grain growth of δ-NiMo compound are discussed on the basis of exothermic reactions between Ni and Mo during diffusional intermixing. The enthalpy of the formation of δ-NiMo is calculated and demonstrated to be sufficient to cause melting/solidification of the compound

Appraisal on Textured Grain Growth and Photoconductivity of ZnO Thin Film SILAR

Directory of Open Access Journals (Sweden)

Deepu Thomas

2014-01-01

Full Text Available ZnO thin films were prepared by successive ionic layer adsorption reaction (SILAR method. The textured grain growth along c-axis in pure ZnO thin films and doped with Sn was studied. The structural analysis of the thin films was done by X-ray diffraction and surface morphology by scanning electron microscopy. Textured grain growth of the samples was measured by comparing the peak intensities. Textured grain growth and photo current in ZnO thin films were found to be enhanced by doping with Sn. ZnO thin film having good crystallinity with preferential (002 orientation is a semiconductor with photonic properties of potential benefit to biophotonics. From energy dispersive X-ray analysis, it is inferred that oxygen vacancy creation is responsible for the enhanced textured grain growth in ZnO thin films.

Statistical mechanics of normal grain growth in one dimension: A partial integro-differential equation model

International Nuclear Information System (INIS)

Ng, Felix S.L.

2016-01-01

We develop a statistical-mechanical model of one-dimensional normal grain growth that does not require any drift-velocity parameterization for grain size, such as used in the continuity equation of traditional mean-field theories. The model tracks the population by considering grain sizes in neighbour pairs; the probability of a pair having neighbours of certain sizes is determined by the size-frequency distribution of all pairs. Accordingly, the evolution obeys a partial integro-differential equation (PIDE) over ‘grain size versus neighbour grain size’ space, so that the grain-size distribution is a projection of the PIDE's solution. This model, which is applicable before as well as after statistically self-similar grain growth has been reached, shows that the traditional continuity equation is invalid outside this state. During statistically self-similar growth, the PIDE correctly predicts the coarsening rate, invariant grain-size distribution and spatial grain size correlations observed in direct simulations. The PIDE is then reducible to the standard continuity equation, and we derive an explicit expression for the drift velocity. It should be possible to formulate similar parameterization-free models of normal grain growth in two and three dimensions.

Growth modes of individual ferrite grains in the austenite to ferrite transformation of low carbon steels

International Nuclear Information System (INIS)

Li, D.Z.; Xiao, N.M.; Lan, Y.J.; Zheng, C.W.; Li, Y.Y.

2007-01-01

The mesoscale deterministic cellular automaton (CA) method and probabilistic Q-state Potts-based Monte Carlo (MC) model have been adopted to investigate independently the individual growth behavior of ferrite grain during the austenite (γ)-ferrite (α) transformation. In these models, the γ-α phase transformation and ferrite grain coarsening induced by α/α grain boundary migration could be simulated simultaneously. The simulations demonstrated that both the hard impingement (ferrite grain coarsening) and the soft impingement (overlapping carbon concentration field) have a great influence on the individual ferrite growth behavior. Generally, ferrite grains displayed six modes of growth behavior: parabolic growth, delayed nucleation and growth, temporary shrinkage, partial shrinkage, complete shrinkage and accelerated growth in the transformation. Some modes have been observed before by the synchrotron X-ray diffraction experiment. The mesoscopic simulation provides an alternative tool for investigating both the individual grain growth behavior and the overall transformation behavior simultaneously during transformation

Effect of additives on enhanced sintering and grain growth in uranium dioxide

International Nuclear Information System (INIS)

Bourgeois, L.

1992-06-01

The use of sintering additives has been the most effective way of promoting grain growth of uranium dioxide. We have established a same mechanism for additives which belongs to corundum structure: chromium, aluminium, vanadium and titanium sesquioxides. Study of thermodynamical stabilities of dopants has lead to define suitable sintering atmospheres in order to enhance grain growth. Low solubility limits have been defined at T=1700 deg C for four additives, from variations of final grain size versus initial dopant concentration Identification of second phase after cooling has been done from electronic diffraction patterns. It appears that these solubilities decrease sharply as positive deviation from stoichiometry of uranium dioxide increases. Dilatometric analysis of sintering of doped uranium dioxide has shown in certain cases some enhancement in densification rates, at the point of onset of abnormal grain growth, which is believed to be the source. Nevertheless, the following growth is accompanied with pores coalescence mechanisms and pores entrapment inside grains. Increased thermal stability, during standard annealing, is expected, limiting thereby redensification of nuclear fuel in reactors. Finally, from investigations of additives vaporizations, Al 2 O 3 and Cr 2 O 3 , oxygen exchanges between additives and matrix are believed to occur, which should lead to enhance pore mobility. (Author)., refs., figs., tabs

Search for grain growth toward the center of L1544

NARCIS (Netherlands)

Chacón-Tanarro, A.; Caselli, P.; Bizzocchi, L.; Pineda, J. E.; Harju, J.; Spaans, M.; Désert, F.-X.

2017-01-01

In dense and cold molecular clouds dust grains are surrounded by thick icy mantles. It is not clear, however, if dust growth and coagulation take place before the protostar switches on. This is an important issue as the presence of large grains may affect the chemical structure of dense cloud cores,

Grain boundary cavity growth under applied stress and internal pressure

International Nuclear Information System (INIS)

Mancuso, J.F.

1977-08-01

The growth of grain boundary cavities under applied stress and internal gas pressure was investigated. Methane gas filled cavities were produced by the C + 4H reversible CH4 reaction in the grain boundaries of type 270 nickel by hydrogen charging in an autoclave at 500 0 C with a hydrogen pressure of either 3.4 or 14.5 MPa. Intergranular fracture of nickel was achieved at a charging temperature of 300 0 C and 10.3 MPa hydrogen pressure. Cavities on the grain boundaries were observed in the scanning electron microscope after fracture. Photomicrographs of the cavities were produced in stereo pairs which were analyzed so as to correct for perspective distortion and also to determine the orientational dependence of cavity growth under an applied tensile stress

Development of n- and p-type Doped Perovskite Single Crystals Using Solid-State Single Crystal Growth (SSCG) Technique

Science.gov (United States)

2017-10-09

for AGG should be minimal. For this purpose, the seeds for AGG may also be provided externally. This process is called the solid-state single...bonding process . Figure 31 shows (a) the growth of one large single crystal from one small single crystal seed as well as (b) the growth of one...one bi-crystal seed : One large bi-crystal can be grown from one small bi-crystal by SSCG process . Fig. 32. Diffusion bonding process for

Simulation study on the growth of grains in dusty plasmas

International Nuclear Information System (INIS)

Sato, Tetsuya; Watanabe, Kunihiko

1997-01-01

A new particle simulation code is developed for studying the dynamics of the grains which are exposed to charging by the background plasma particles. Effects of regular attachment of electrons and ions, effects of secondary electron emission, and coagulation of grains are included in this code. Simulation results show that grains randomly change their charges from negative to positive, or from positive to negative in a 'flip-flop' fashion as a result of competition between the electron attachment and secondary electron emission. It is found that the flip-flop effect becomes remarkable when the radius of grains is of the order of 10 nm, because the attachment of a single electron to a grain is less effective on the surface potential for larger grains, while the average probability of electron attachment is smaller for smaller grains. Grains with opposite charges attract each other to coagulate, so that grains of size of 10 nm are likely to grow in size. The flip-flop effect is found to be essential to the growth of grains. (author)

Yttria-Ceria stabilized tetragonal zirconia polycrystals: Sintering, grain growth and grain boundary segregation

NARCIS (Netherlands)

Boutz, M.M.R.; Boutz, M.M.R.; Winnubst, Aloysius J.A.; Burggraaf, Anthonie; Burggraaf, A.J.

1994-01-01

An analysis is presented of grain growth and densification of yttria-ceria stabilized tetragonal zirconia polycrystals (Y, Ce-TZPs) using both isothermal and non-isothermal techniques. The characteristics of Y, Ce-TZPs are compared to those of Y-TZP and Ce-TZP and the effect of increasing ceria

Densification and Grain Growth in Polycrystalline Olivine Rocks Synthesized By Evacuated Hot-Pressing

Science.gov (United States)

Meyers, C. D.; Kohlstedt, D. L.; Zimmerman, M. E.

2017-12-01

Experiments on laboratory-synthesized olivine-rich rocks form the starting material for many investigations of physical processes in the Earth's upper mantle (e.g., creep behavior, ionic diffusion, and grain growth). Typically, a fit of a constitutive law to experimental data provides a description of the kinetics of a process needed to extrapolate across several orders of magnitude from laboratory to geological timescales. Although grain-size is a critical parameter in determining physical properties such as viscosity, broad disagreement persists amongst the results of various studies of grain growth kinetics in olivine-rich rocks. Small amounts of impurities or porosity dramatically affect the kinetics of grain growth. In this study, we developed an improved method for densifying olivine-rich rocks fabricated from powdered, gem-quality single crystals that involves evacuating the pore space, with the aim of refining measurements of the kinetics of mantle materials. In previous studies, olivine powders were sealed in a metal can and hydrostatically annealed at roughly 300 MPa and 1250 °C. These samples, which appear opaque and milky-green, typically retain a small amount of porosity. Consequently, when annealed at 1 atm, extensive pore growth occurs, inhibiting grain growth. In addition, Fourier-transform infrared and confocal Raman spectroscopy reveal absorption peaks characteristic of CO2 in the pores of conventionally hot-pressed material. To avoid trapping of adsorbed contaminants, we developed an evacuated hot-pressing method, wherein the pore space of powder compacts is vented to vacuum during heating and pressurization. This method produces a highly dense, green-tinted, transparent material. No CO2 absorptions peaks exist in evacuated hot-pressed material. When reheated to annealing temperatures at 1 atm, the evacuated hot-pressed material undergoes limited pore growth and dramatically enhanced grain-growth rates. High-strain deformation experiments on

Effect of Strain Restored Energy on Abnormal Grain Growth in Mg Alloy Simulated by Phase Field Methods

Science.gov (United States)

Wu, Yan; Huang, Yuan-yuan

2018-03-01

Abnormal grain growth of single phase AZ31 Mg alloy in the spatio-temporal process has been simulated by phase field models, and the influencing factors of abnormal grain growth are studied in order to find the ways to control secondary recrystallization in the microstructure. The study aims to find out the mechanisms for abnormal grain growth in real alloys. It is shown from the simulated results that the abnormal grain growth can be controlled by the strain restored energy. Secondary recrystallization after an annealing treatment can be induced if there are grains of a certain orientation in the microstructure with local high restored energy. However, if the value of the local restored energy at a certain grain orientation is not greater than 1.1E 0, there may be no abnormal grain growth in the microstructure.

[The Swedish ambulance services 1935-1936 of Gunnar Agge].

Science.gov (United States)

Gustavsson, Pär; Nilsson, Peter M

2006-01-01

The fact that Sweden has been spared from war on its soil for almost 200 years, has not stopped Swedish citizens from participating in conflicts worldwide during this period. This has been described, especially from the soldiers perspective. The contribution of Swedish physicians has not been written about to the same extent. When Mussolini's Italy in October 1935 invaded the poor and underdeveloped country of Ethiopia (former Abyssinia) an ambulance was immediately organized by the Swedish Red Cross. To lead such an expedition, a great knowledge of Ethiopian culture och maybe most importantly, of the weather and geographical conditions, was undoubtedly demanded. Therefore, the Swedish Red Cross turned to two Ethiopian veterans. Doctor Fride Hylander, a missionary-son who had been working on a hospital project in the Ethiopian province of Harrar and his friend since school years, doctor Gunnar Agge, were assigned the leadership of the ambulance. Dr Agge had also participated in improving the Ethiopian health care both in Harrar and later as civilian and military doctor in the province of Ogaden, where he was medically responsible for the more than 9 000 men strong army that the Ethiopian emperor had stationed there after Italian provocations. Most of the other members of the ambulance were handpicked by these two leaders and many of them had, just like themselves, a stong religious belief. A money-raise was immediately initiated and in less than six weeks 700 000 Swedish crowns had been collected, more then twice the sum the ambulance was calculated to cost. In early november 1935 the ambulance was clear to go. Their primary objective was to travel through British Somaliland and establish a field-hospital in the province of Harrar. However, the Ethiopian emperor had other things in mind. He wanted to reorganize the ambulance and divide it in two and place it closer to the front line. The ambulance decided to go along with his wish. Both groups started eventually

Carex flava agg. (section Ceratocystis, Cyperaceae in Poland: taxonomy, morphological variation, and soil conditions

Directory of Open Access Journals (Sweden)

Więcław Helena

2014-03-01

Full Text Available Sedges of Carex flava agg., typical of moist or wet habitats, are difficult to classify because of a lack of clear-cut morphological differences between them and the existence of numerous hybrids. This monograph presents results of research conducted in 2007-2012 in various parts of Poland. The plant material consisted of 1852 living specimens of Carex flava agg., collected from 80 localities, and dried specimens from 26 herbaria and from 7 private collections. The analysis involved 45 morphological characters (34 quantitative and 11 qualitative and 9 soil parameters. Univariate, bivariate, and multivariate statistical methods were used to process the data. The results confirm the taxonomic classification dividing the C. flava group into 4 species: C. flava s.s., C. lepidocarpa, C. demissa, and C. viridula. This classification is based on (i a high observed level of morphological separation of these taxa, resulting mostly from differences in generative characters, i.e. length of the utricle and its beak, and percentage ratio of beak length to total utricle length; (ii integrity of the taxa at the sites where they coexist, although some intermediate forms resulting from hybridization are also present; (iii habitat preferences of the taxa, especially the preference of C. lepidocarpa for calcareous sites and of C. demissa for slightly acidic soils. Thus in Poland the analysed taxa are morphologically well-defined and show clear ecological preferences. Continuous variation of morphological characters was observed among specimens of C. viridula, so it is not justifiable to distinguish its subspecies (sometimes classified even as separate species, described previously in literature. Consequently, the 2 subgroups of C. viridula were treated as local variants (i.e. varieties: var. viridula and var. pulchella, considering their different habitat requirements. Additionally, 5 hybrids were distinguished within C. flava agg.: C. ×alsatica [= C. demissa �

Analysis of grain growth process in melt spun Fe-B alloys under the initial saturated grain boundary segregation condition

International Nuclear Information System (INIS)

Chen, Z.; Liu, F.; Yang, X.Q.; Fan, Y.; Shen, C.J.

2012-01-01

Highlights: → We compared pure kinetic, pure thermodynamic and extended thermo-kinetic models. → An initial saturated GB segregation condition of nanoscale Fe-B alloys was determined. → The controlled-mechanism was proposed using two characteristic times (t 1 and t 2 ). - Abstract: A grain growth process in the melt spun low-solid-solubility Fe-B alloys was analyzed under the initial saturated grain boundary (GB) segregation condition. Applying melt spinning technique, single-phase supersaturated nanograins were prepared. Grain growth behavior of the single-phase supersaturated nanograins was investigated by performing isothermal annealing at 700 deg. C. Combined with the effect of GB segregation on the initial GB excess amount, the thermo-kinetic model [Chen et al., Acta Mater. 57 (2009) 1466] was extended to describe the initial GB segregation condition of nanoscale Fe-B alloys. In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, an initial saturated GB segregation condition was determined. The controlled-mechanism of grain growth under initial saturated GB segregation condition was proposed using two characteristic annealing times (t 1 and t 2 ), which included a mainly kinetic-controlled process (t ≤ t 1 ), a transition from kinetic-mechanism to thermodynamic-mechanism (t 1 2 ) and pure thermodynamic-controlled process (t ≥ t 2 ).

A grain boundary sliding model for cavitation, crack growth and ...

African Journals Online (AJOL)

A model is presented for cavity growth, crack propagation and fracture resulting from grain boundary sliding (GBS) during high temperature creep deformation. The theory of cavity growth by GBS was based on energy balance criteria on the assumption that the matrix is sufficiently plastic to accommodate misfit strains ...

A Model of Silicate Grain Nucleation and Growth in Circumstellar Outflows

Science.gov (United States)

Paquette, John A.; Ferguson, Frank T.; Nuth, Joseph A., III

2011-01-01

Based on its abundance, high bond energy, and recent measurements of its vapor pressure SiO is a natural candidate for dust nucleation in circumstellar outflows around asymptotic giant branch stars. In this paper, we describe a model of the nucleation and growth of silicate dust in such outflows. The sensitivity of the model to varying choices of poorly constrained chemical parameters is explored, and the merits of using scaled rather than classical nucleation theory are briefly considered, An elaboration of the model that includes magnesium and iron as growth species is then presented and discussed. The composition of the bulk of the grains derived from the model is consistent with olivines and pyroxenes, but somewhat metal-rich grains and very small, nearly pure SiO grains are also produced,

Short-time beta grain growth kinetics for a conventional titanium alloy

International Nuclear Information System (INIS)

Semiatin, S.L.; Sukonnik, I.M.

1996-01-01

The kinetics of beta grain growth during short-time, supertransus heat treatment of Ti-5Al-4V were determined using a salt-pot technique. The finite-time, subtransus temperature transient during salt-pot heating was quantified through measurements of the heat transfer coefficient characterizing conduction across the salt-titanium interface and a simple heat conduction analysis which incorporated this heat transfer coefficient. Grain size versus time data adjusted to account for the subtransus temperature transient were successfully fit to the parabolic grain growth law d n - d 0 n = kt exp(-Q/RT) using an exponent n equal to 2.0. Comparison of the present results to rapid, continuous heat treatment data in the literature for a similar titanium alloy revealed a number of semi-quantitative similarities

The effect of dielectric constants on noble metal/semiconductor SERS enhancement: FDTD simulation and experiment validation of Ag/Ge and Ag/Si substrates.

Science.gov (United States)

Wang, Tao; Zhang, Zhaoshun; Liao, Fan; Cai, Qian; Li, Yanqing; Lee, Shuit-Tong; Shao, Mingwang

2014-02-11

The finite-difference time-domain (FDTD) method was employed to simulate the electric field distribution for noble metal (Au or Ag)/semiconductor (Ge or Si) substrates. The simulation showed that noble metal/Ge had stronger SERS enhancement than noble metal/Si, which was mainly attributed to the different dielectric constants of semiconductors. In order to verify the simulation, Ag nanoparticles with the diameter of ca. 40 nm were grown on Ge or Si wafer (Ag/Ge or Ag/Si) and employed as surface-enhanced Raman scattering substrates to detect analytes in solution. The experiment demonstrated that both the two substrates exhibited excellent performance in the low concentration detection of Rhodamine 6G. Besides, the enhancement factor (1.3 × 10(9)) and relative standard deviation values (less than 11%) of Ag/Ge substrate were both better than those of Ag/Si (2.9 × 10(7) and less than 15%, respectively), which was consistent with the FDTD simulation. Moreover, Ag nanoparticles were grown in-situ on Ge substrate, which kept the nanoparticles from aggregation in the detection. To data, Ag/Ge substrates showed the best performance for their sensitivity and uniformity among the noble metal/semiconductor ones.

Morphology and grain structure evolution during epitaxial growth of Ag films on native-oxide-covered Si surface

International Nuclear Information System (INIS)

Hur, Tae-Bong; Kim, Hong Koo; Perello, David; Yun, Minhee; Kulovits, Andreas; Wiezorek, Joerg

2008-01-01

Epitaxial nanocrystalline Ag films were grown on initially native-oxide-covered Si(001) substrates using radio-frequency magnetron sputtering. Mechanisms of grain growth and morphology evolution were investigated. An epitaxially oriented Ag layer (∼5 nm thick) formed on the oxide-desorbed Si surface during the initial growth phase. After a period of growth instability, characterized as kinetic roughening, grain growth stagnation, and increase of step-edge density, a layer of nanocrystalline Ag grains with a uniform size distribution appeared on the quasi-two-dimensional layer. This hierarchical process of film formation is attributed to the dynamic interplay between incoming energetic Ag particles and native oxide. The cyclic interaction (desorption and migration) of the oxide with the growing Ag film is found to play a crucial role in the characteristic evolution of grain growth and morphology change involving an interval of grain growth stagnation

Experimental studies of Micro- and Nano-grained UO₂: Grain Growth Behavior, Sufrace Morphology, and Fracture Toughness

Energy Technology Data Exchange (ETDEWEB)

Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States); Mo, Kun [Argonne National Lab. (ANL), Argonne, IL (United States); Jamison, Laura M. [Argonne National Lab. (ANL), Argonne, IL (United States); Lian, Jie [Rensselaer Polytechnic Inst., Troy, NY (United States); Yao, Tiankai [Rensselaer Polytechnic Inst., Troy, NY (United States); Bhattacharya, Sumit [Argonne National Lab. (ANL), Argonne, IL (United States); Northwestern Univ., Evanston, IL (United States)

2016-01-01

This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructure-based materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize the experimental efforts in FY16 including the following important experiments: (1) in-situ grain growth measurement of nano-grained UO₂; (2) investigation of surface morphology in micrograined UO₂; (3) Nano-indentation experiments on nano- and micro-grained UO₂. The highlight of this year is: we have successfully demonstrated our capability to in-situ measure grain size development while maintaining the stoichiometry of nano-grained UO₂ materials; the experiment is, for the first time, using synchrotron X-ray diffraction to in-situ measure grain growth behavior of UO₂.

Residual-stress-induced grain growth of twinned grains and its effect on formability of magnesium alloy sheet at room temperature

Energy Technology Data Exchange (ETDEWEB)

Kim, Se-Jong [Korea Institute of Material Science, 66 Sangnam-dong, C-si, Gyeongnam 641-831 (Korea, Republic of); Kim, Daeyong, E-mail: daeyong@kims.re.kr [Korea Institute of Material Science, 66 Sangnam-dong, C-si, Gyeongnam 641-831 (Korea, Republic of); Lee, Keunho; Cho, Hoon-Hwe; Han, Heung Nam [Department of Materials Science and Engineering and RIAM, Seoul National University, Seoul 151-744 (Korea, Republic of)

2015-11-15

A magnesium alloy sheet was subjected to in-plane compression along with a vertical load to avoid buckling during compression. Pre-compressed specimens machined from the sheet were annealed at different temperatures and the changes in microstructure and texture were observed using electron back scattered diffraction (EBSD). Twinned grains preferentially grew during annealing at 300 °C, so that a strong texture with the < 0001 > direction parallel to the transverse direction developed. EBSD analysis confirmed that the friction caused by the vertical load induced inhomogeneous distribution of residual stress, which acted as an additional driving force for preferential grain growth of twinned grain during annealing. The annealed specimen showed excellent formability. - Highlights: • A magnesium alloy sheet subjected to in-plane compression under a vertical load • The vertical load induced inhomogeneous distribution of the residual stress. • The residual stress acted as an additional driving force for grain growth. • The annealed specimen with strong non-basal texture showed excellent formability.

Identification of Accretion as Grain Growth Mechanism in Astrophysically Relevant Water&ice Dusty Plasma Experiment

Science.gov (United States)

Marshall, Ryan S.; Chai, Kil-Byoung; Bellan, Paul M.

2017-03-01

The grain growth process in the Caltech water-ice dusty plasma experiment has been studied using a high-speed camera and a long-distance microscope lens. It is observed that (I) the ice grain number density decreases fourfold as the average grain major axis increases from 20 to 80 μm, (II) the major axis length has a log-normal distribution rather than a power-law dependence, and (III) no collisions between ice grains are apparent. The grains have a large negative charge resulting in strong mutual repulsion and this, combined with the fractal character of the ice grains, prevents them from agglomerating. In order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains, the volumetric packing factor (I.e., ratio of the actual volume to the volume of a circumscribing ellipsoid) of the ice grains must be less than ˜0.1 depending on the exact relative velocity of the grains in question. Thus, it is concluded that direct accretion of water molecules is very likely to dominate the observed ice grain growth.

Identification of Accretion as Grain Growth Mechanism in Astrophysically Relevant Water–Ice Dusty Plasma Experiment

Energy Technology Data Exchange (ETDEWEB)

Marshall, Ryan S.; Chai, Kil-Byoung; Bellan, Paul M. [Applied Physics and Materials Science, Caltech, Pasadena, CA 91125 (United States)

2017-03-01

The grain growth process in the Caltech water–ice dusty plasma experiment has been studied using a high-speed camera and a long-distance microscope lens. It is observed that (i) the ice grain number density decreases fourfold as the average grain major axis increases from 20 to 80 μ m, (ii) the major axis length has a log-normal distribution rather than a power-law dependence, and (iii) no collisions between ice grains are apparent. The grains have a large negative charge resulting in strong mutual repulsion and this, combined with the fractal character of the ice grains, prevents them from agglomerating. In order for the grain kinetic energy to be sufficiently small to prevent collisions between ice grains, the volumetric packing factor (i.e., ratio of the actual volume to the volume of a circumscribing ellipsoid) of the ice grains must be less than ∼0.1 depending on the exact relative velocity of the grains in question. Thus, it is concluded that direct accretion of water molecules is very likely to dominate the observed ice grain growth.

Nanoscale grain growth behaviour of CoAl intermetallic synthesized ...

Indian Academy of Sciences (India)

Grain growth behaviour of the nanocrystalline CoAl intermetallic compound synthesized by mechanical alloying has been studied by isothermal annealing at different temperatures and durations. X-ray diffraction method was employed to investigate structural evolutions during mechanical alloying and annealing processes.

Nanoscale grain growth behaviour of CoAl intermetallic synthesized ...

Indian Academy of Sciences (India)

Administrator

Abstract. Grain growth behaviour of the nanocrystalline CoAl intermetallic compound synthesized by mechanical alloying has been studied by isothermal annealing at different temperatures and durations. X-ray diffraction method was employed to investigate structural evolutions during mechanical alloying and anneal-.

Repeated growth and bubbling transfer of graphene with millimetre-size single-crystal grains using platinum.

Science.gov (United States)

Gao, Libo; Ren, Wencai; Xu, Huilong; Jin, Li; Wang, Zhenxing; Ma, Teng; Ma, Lai-Peng; Zhang, Zhiyong; Fu, Qiang; Peng, Lian-Mao; Bao, Xinhe; Cheng, Hui-Ming

2012-02-28

Large single-crystal graphene is highly desired and important for the applications of graphene in electronics, as grain boundaries between graphene grains markedly degrade its quality and properties. Here we report the growth of millimetre-sized hexagonal single-crystal graphene and graphene films joined from such grains on Pt by ambient-pressure chemical vapour deposition. We report a bubbling method to transfer these single graphene grains and graphene films to arbitrary substrate, which is nondestructive not only to graphene, but also to the Pt substrates. The Pt substrates can be repeatedly used for graphene growth. The graphene shows high crystal quality with the reported lowest wrinkle height of 0.8 nm and a carrier mobility of greater than 7,100 cm(2) V(-1) s(-1) under ambient conditions. The repeatable growth of graphene with large single-crystal grains on Pt and its nondestructive transfer may enable various applications.

A simple method to evaluate the fission gas release at fuel grain boundary including the grain growth both at constant and at transient power histories

International Nuclear Information System (INIS)

Paraschiv, M.; Paraschiv, A.

1991-01-01

A method to rewrite Fick's second law for a region with a moving boundary when the moving law in time of this boundary is known, has been proposed. This method was applied to Booth's sphere model for radioactive and stable fission product diffusion from the oxide fuel grain in order to take into account the grain growth. The solution of this new equation was presented in the mathematical formulation for power histories from ANS 5.4 model for the stable species. It is very simple to apply and very accurate. The results obtained with this solution for constant and transient temperatures show that the fission gas release (FGR) at grain boundary is strongly dependent on kinetics of grain growth. The utilization of two semiempirical grain growth laws, from published information, shows that the fuel microstructural properties need to be multicitly considered in the fission gas release for every manufacturer of fuel. (orig.)

Influence of Different Growth Conditions on the Kefir Grains Production, used in the Kefiran Synthesis

Directory of Open Access Journals (Sweden)

Carmen Rodica Pop

2014-11-01

Full Text Available The purpose of this study was to optimize the kefir grains biomass production, using milk as culture media. The kefir grains were cultured at different changed conditions (temperature, time, shaker rotating speed, culture media supplemented to evaluate their effects. Results showed that optimal culture conditions were using the organic skim milk, incubated at 25°C for 24 hours with a rotation rate of 125 rpm. According to results, the growth rate was 38.9 g/L for 24 h, at 25°C using the organic milk - OSM, 36.87 g/L during 24 hours, optimal time for propagation process gave 37.93 g/L kefir grains biomass when the effect of temperature level was tested. The homogenization of medium with shaker rotating induced a greater growth rate, it was obtained 38.9 g/L for 24 h, at 25°C using rotation rate at 125 rpm. The growing medium (conventional milk supplemented with different minerals and vitamins may lead to improve the growth conditions of kefir grains biomass. The optimization of the growth environment is very important for achieving the maximum production of kefir grains biomass, substrate necessary to obtain the polysaccharide kefiran

EFFECT OF SOME PLANT GROWTH REGULATORS WITH RETARDING ACTIVITY ON SPRING PEA FOR GRAIN

Directory of Open Access Journals (Sweden)

Tsenka ZHELYAZKOVA

2012-12-01

Full Text Available A field experiment was conducted at Trakia University - Stara Zagora to establish the effect of some growth retardants on morphological and productive parameters in spring pea for grain variety Bogatir. Three combined preparations: Trisalvit (phenylphthalamic acid + chlorocholine chloride + chlorophenoxyacetic acid +salicylic acid at doses of 300 and 400 сmз*ha-1; SM-21 (phenylphthalamic acid + chlorocholine chloride at doses of 300 and 400 сmз*ha-1 and PNSA-44 (phenylphthalamic acid + naphthaleneacetic acid + chlorophenoxyacetic acid at doses of 200 and 300 сmз*ha-1 were applied in the early growth phase of the plant up to a height of 15-20 cm. The study showed that the greatest reduction in the stem height (by 12.8% compared to untreated plants was achieved by applying SM-21 (400 сmз*ha-1. The application of growth regulators Trisalvit and SM-21 had no appreciable effect on the production of spring pea grain. Maximum values of yield structure components (number of pods and grain per plant, grain mass per plant and mass of 1000 grain and the yield were obtained after application of PNSA-44 (300 сmз*ha-1 - up to 5.6% (117.2 kg*ha-1 more grain than the control. The investigation of the influence of tested factors (retardant, dose and year demonstrated that the conditions of the year as a factor had the strongest effect on plant height and grain yield.

Austenite grain growth and microstructure control in simulated heat affected zones of microalloyed HSLA steel

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lei [Department of Machine Tools and Factory Management, Technical University of Berlin, Pascalstraße 8 – 9, 10587, Berlin (Germany); Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Kannengiesser, Thomas [Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Institute of Materials and Joining Technology, Otto von Guericke University Magdeburg, Universitetsplatz 2, 39106, Magdeburg (Germany)

2014-09-08

The roles of microalloying niobium, titanium and vanadium for controlling austenite grain growth, microstructure evolution and hardness were investigated at different simulated heat affected zones (HAZ) for high strength low alloy (HSLA) S690QL steel. High resolution FEG-SEM has been used to characterize fine bainitic ferrite, martensite and nanosized second phases at simulated coarse and fine grain HAZs. It was found that for Ti bearing steel (Ti/N ratio is 2) austenite grain had the slowest growth rate due to the presence of most stable TiN. The fine cuboidal particles promoted intragranular acicular ferrite (IGF) formation. Nb bearing steel exhibited relatively weaker grain growth retardation compared with titanium bearing steels and a mixed microstructure of bainite and martensite was present for all simulated HAZs. IGF existed at coarse grain HAZ of Ti+V bearing steel but it was totally replaced by bainite at fine grain HAZs. Hardness result was closely related to the morphology of bainitic ferrite, intragranular ferrite and second phases within ferrite. The microstructure and hardness results of different simulated HAZs were in good agreement with welded experimental results.

The diffusional growth of a grain boundary crack

International Nuclear Information System (INIS)

Puls, M.P.; Dutton, R.

1977-10-01

This report considers the possibility of high temperature rupture occurring by a grain boundary diffusional mechanism. It is assumed that a pre-existing, intergranular crack grows by loss of atoms from the crack tip to the grain boundary. Rupture occurs when the crack has grown to a critical length. A theoretical treatment of the kinetics of crack growth is presented and equations are derived for the crack velocity and time to rupture. A comparison is made with a previous theoretical model developed by Charles, together with rupture data obtained experimentally for the nickel-based alloy, Nimonic 80A. We conclude that experimental verification of the theoretical models requires a comparison with crack velocity data rather than time to rupture data. (author)

Irreversible thermodynamics, parabolic law and self-similar state in grain growth

International Nuclear Information System (INIS)

Rios, P.R.

2004-01-01

The formalism of the thermodynamic theory of irreversible processes is applied to grain growth to investigate the nature of the self-similar state and its corresponding parabolic law. Grain growth does not reach a steady state in the sense that the entropy production remains constant. However, the entropy production can be written as a product of two factors: a scale factor that tends to zero for long times and a scaled entropy production. It is suggested that the parabolic law and the self-similar state may be associated with the minimum of this scaled entropy production. This result implies that the parabolic law and the self-similar state have a sound irreversible thermodynamical basis

Growth, assimilate partitioning and grain yield response of soybean ...

African Journals Online (AJOL)

This investigation tested variation in the growth components, assimilate partitioning and grain yield of soybean (Glycine max L. Merrrill) varieties established in CO2 enriched atmosphere when inoculated with mixtures of Arbuscular mycorrhizal fungi (AMF) species in the humid rainforest of Nigeria. A pot and a field ...

The destruction and growth of dust grains in interstellar space

International Nuclear Information System (INIS)

Barlow, M.J.

1978-01-01

The processes governing the destruction and growth of dust grains in interstellar space are investigated with a view to establishing the conditions required for the existence of ice mantles. In this paper sputtering by particles with energies in the eV to GeV range is considered. Previous sputtering yield estimates which were based on theoretical considerations are shown to be greatly in error for incident particle energies of less than 1 keV. Empirical formulae for the sputtering threshold energy and the sputtering yield are derived from the extensive experimental data available. The sputtering of grains in H II regions, in the inter-cloud medium, and in shock waves produced by cloud-cloud collisions and by supernova remnants, is investigated. Of these, supernova remnants are shown to be the most important, leading to lifetimes of approximately 2 x 10 8 yr for ice grains and between 5 to 20 x 10 8 yr for refractory grains. Destruction rates are estimated for grains bombarded by MeV and GeV cosmic rays. It is shown that collision cascade sputtering dominates evaporative sputtering produced by thermal spikes. It is also shown that even if all electron excitation energy loss in a grain material could be transferred to the lattice particles, the observed cosmic ray flux spectrum could not cause significant destruction of ice grains. (author)

Theory and modeling of microstructural evolution in polycrystalline materials: Solute segregation, grain growth and phase transformations

Science.gov (United States)

Ma, Ning

2005-11-01

To accurately predict microstructure evolution and, hence, to synthesis metal and ceramic alloys with desirable properties involves many fundamental as well as practical issues. In the present study, novel theoretical and phase field approaches have been developed to address some of these issues including solute drag and segregation transition at grain boundaries and dislocations, grain growth in systems of anisotropic boundary properties, and precipitate microstructure development in polycrystalline materials. The segregation model has allowed for the prediction of a first-order segregation transition, which could be related to the sharp transition of solute concentration of grain boundary as a function of temperature. The incorporating of interfacial energy and mobility as functions of misorientation and inclination in the phase field model has allowed for the study of concurrent grain growth and texture evolution. The simulation results were analyzed using the concept of local grain boundary energy density, which simplified significantly the development of governing equations for texture controlled grain growth in Ti-6Al-4V. Quantitative phase field modeling techniques have been developed by incorporating thermodynamic and diffusivity databases. The models have been validated against DICTRA simulations in simple 1D problems and applied to simulate realistic microstructural evolutions in Ti-6Al-4V, including grain boundary a and globular a growth and sideplate development under both isothermal aging and continuous cooling conditions. The simulation predictions agree well with experimental observations.

Evolution of the Annealing Twin Density during δ-Supersolvus Grain Growth in the Nickel-Based Superalloy Inconel™ 718

Directory of Open Access Journals (Sweden)

Yuan Jin

2015-12-01

Full Text Available Grain growth experiments were performed on Inconel™ 718 to investigate the possible correlation of the annealing twin density with grain size and with annealing temperature. Those experiments were conducted at different temperatures in the δ supersolvus domain and under such conditions that only capillarity forces were involved in the grain boundary migration process. In the investigated range, there is a strong inverse correlation of the twin density with the average grain size. On the other hand, the twin density at a given average grain size is not sensitive to annealing temperature. Consistent with previous results for pure nickel, the twin density evolution in Inconel™ 718 is likely to be mainly controlled by the propagation of the pre-existing twins of the growing grains; i.e., the largest ones of the initial microstructure. Almost no new twin boundaries are created during the grain growth process itself. Therefore, the twin density at a given average grain size is mainly dependent on the twin density in the largest grains of the initial microstructure and independent of the temperature at which grains grow. Based on the observations, a mean field model is proposed to predict annealing twin density as a function of grain size during grain growth.

A multiscale coupled finite-element and phase-field framework to modeling stressed grain growth in polycrystalline thin films

Energy Technology Data Exchange (ETDEWEB)

Jamshidian, M., E-mail: jamshidian@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar (Germany); Thamburaja, P., E-mail: prakash.thamburaja@gmail.com [Department of Mechanical & Materials Engineering, Universiti Kebangsaan Malaysia (UKM), Bangi 43600 (Malaysia); Rabczuk, T., E-mail: timon.rabczuk@tdt.edu.vn [Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City (Viet Nam); Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City (Viet Nam)

2016-12-15

A previously-developed finite-deformation- and crystal-elasticity-based constitutive theory for stressed grain growth in cubic polycrystalline bodies has been augmented to include a description of excess surface energy and grain-growth stagnation mechanisms through the use of surface effect state variables in a thermodynamically-consistent manner. The constitutive theory was also implemented into a multiscale coupled finite-element and phase-field computational framework. With the material parameters in the constitutive theory suitably calibrated, our three-dimensional numerical simulations show that the constitutive model is able to accurately predict the experimentally-determined evolution of crystallographic texture and grain size statistics in polycrystalline copper thin films deposited on polyimide substrate and annealed at high-homologous temperatures. In particular, our numerical analyses show that the broad texture transition observed in the annealing experiments of polycrystalline thin films is caused by grain growth stagnation mechanisms. - Graphical abstract: - Highlights: • Developing a theory for stressed grain growth in polycrystalline thin films. • Implementation into a multiscale coupled finite-element and phase-field framework. • Quantitative reproduction of the experimental grain growth data by simulations. • Revealing the cause of texture transition to be due to the stagnation mechanisms.

Quantitative Phase-Field Approach for Simulating Grain Growth in Anisotropic Systems with Arbitrary Inclination and Misorientation Dependence

International Nuclear Information System (INIS)

Moelans, N.; Blanpain, B.; Wollants, P.

2008-01-01

A phase-field approach for quantitative simulations of grain growth in anisotropic systems is introduced, together with a new methodology to derive appropriate model parameters that reproduce given misorientation and inclination dependent grain boundary energy and mobility in the simulations. The proposed model formulation and parameter choice guarantee a constant diffuse interface width and consequently give high controllability of the accuracy in grain growth simulations

Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples

Science.gov (United States)

Suslova, A.; El-Atwani, O.; Sagapuram, D.; Harilal, S. S.; Hassanein, A.

2014-11-01

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten.

Grain growth behavior of Li{sub 4}SiO{sub 4} pebbles fabricated by agar method for tritium breeder

Energy Technology Data Exchange (ETDEWEB)

Xiang, Maoqiao [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 (China); Zhang, Yingchun, E-mail: zycustb@126.com [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 (China); Zhang, Yun; Wang, Chaofu; Liu, Wei [School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 (China); Yu, Yonghong [Department of Physics, Renmin University of China, Beijing, 100872 (China)

2016-11-15

Highlights: • Grain sizes of Li{sub 4}SiO{sub 4} were adjusted by different silicon sources. • Grain growth exponent of Li{sub 4}SiO{sub 4} was about 3. • Grain growth activation energy of Li{sub 4}SiO{sub 4} was about 125.54 kJ/mol. • Grain growth of Li{sub 4}SiO{sub 4} pebble was controlled by vapor transport. - Abstract: The Li{sub 4}SiO{sub 4} tritium breeding pebbles will be filled in the blanket and used for 2 years or more at high temperatures, which would increase the grain size and affect tritium release. Hence, grain sizes of the Li{sub 4}SiO{sub 4} pebbles fabricated by agar method were investigated, and two kinds of different silicon sources (crystal and amorphous SiO{sub 2}) with different particle sizes were used. The particle size of SiO{sub 2} could affect grain size and density of the Li{sub 4}SiO{sub 4} pebble. And the isothermal sintering was carried out to study the grain growth kinetics of Li{sub 4}SiO{sub 4}. The grain growth exponent (n) and the activation energy (Q) were calculated by the phenomenological kinetic equation. The calculated n values were 4.10, 3.98, 3.34 and 2.96, and corresponding Q values were 152.15, 147.99, 125.54 and 110.58 kJ/mol, respectively. At the higher sintering temperatures (950 and 1000 °C), the grain growth of Li{sub 4}SiO{sub 4} was controlled by vapor transport.

Grain growth competition during thin-sample directional solidification of dendritic microstructures: A phase-field study

International Nuclear Information System (INIS)

Tourret, D.; Song, Y.; Clarke, A.J.; Karma, A.

2017-01-01

We present the results of a comprehensive phase-field study of columnar grain growth competition in bi-crystalline samples in two dimensions (2D) and in three dimensions (3D) for small sample thicknesses allowing a single row of dendrites to form. We focus on the selection of grain boundary (GB) orientation during directional solidification in the steady-state dendritic regime, and study its dependence upon the orientation of two competing grains. In 2D, we map the entire orientation range for both grains, performing several simulations for each configuration to account for the stochasticity of GB orientation selection and to assess the average GB behavior. We find that GB orientation selection depends strongly on whether the primary dendrite growth directions have lateral components (i.e. components perpendicular to the axis of the temperature gradient) that point in the same or opposite directions in the two grains. We identify a range of grain orientations in which grain selection follows the classical description of Walton and Chalmers. We also identify conditions that favor unusual overgrowth of favorably-oriented dendrites at a converging GB. We propose a simple analytical description that reproduces the average GB orientation selection from 2D simulations within statistical fluctuations of a few degrees. In 3D, we find a similar GB orientation selection as in 2D when secondary branches grow in planes parallel and perpendicular to the sample walls. Remarkably, quasi-2D behavior is also observed even when those perpendicular sidebranching planes are rotated by a finite azimuthal angle about the primary dendrite growth axis as long as the absolute values of those azimuthal angles are equal in both grains. In contrast, when the absolute values of those azimuthal angles differ markedly, we find that unusual overgrowth events at a converging GB are promoted by a high azimuthal angle in the least-favorably-oriented grain. We also find that diverging GBs can be

Creep crack growth by grain boundary cavitation under monotonic and cyclic loading

Science.gov (United States)

Wen, Jian-Feng; Srivastava, Ankit; Benzerga, Amine; Tu, Shan-Tung; Needleman, Alan

2017-11-01

Plane strain finite deformation finite element calculations of mode I crack growth under small scale creep conditions are carried out. Attention is confined to isothermal conditions and two time histories of the applied stress intensity factor: (i) a monononic increase to a plateau value subsequently held fixed; and (ii) a cyclic time variation. The crack growth calculations are based on a micromechanics constitutive relation that couples creep deformation and damage due to grain boundary cavitation. Grain boundary cavitation, with cavity growth due to both creep and diffusion, is taken as the sole failure mechanism contributing to crack growth. The influence on the crack growth rate of loading history parameters, such as the magnitude of the applied stress intensity factor, the ratio of the applied minimum to maximum stress intensity factors, the loading rate, the hold time and the cyclic loading frequency, are explored. The crack growth rate under cyclic loading conditions is found to be greater than under monotonic creep loading with the plateau applied stress intensity factor equal to its maximum value under cyclic loading conditions. Several features of the crack growth behavior observed in creep-fatigue tests naturally emerge, for example, a Paris law type relation is obtained for cyclic loading.

Stress-driven grain growth

CSIR Research Space (South Africa)

Nabarro, FRN

1998-11-13

Full Text Available of length b (1+ epsilon) is parallel to sigma, embedded in a grain in which the lattice vector b (1+ epsilon) is transverse to sigma. If the embedded grain grows at the expense of its matrix, the source of the stress will do work, and therefore the presence...

Computer simulation of 2D grain growth using a cellular automata model based on the lowest energy principle

International Nuclear Information System (INIS)

He Yizhu; Ding Hanlin; Liu Liufa; Shin, Keesam

2006-01-01

The morphology, topology and kinetics of normal grain growth in two-dimension were studied by computer simulation using a cellular automata (Canada) model based on the lowest energy principle. The thermodynamic energy that follows Maxwell-Boltzmann statistics has been introduced into this model for the calculation of energy change. The transition that can reduce the system energy to the lowest level is chosen to occur when there is more than one possible transition direction. The simulation results show that the kinetics of normal grain growth follows the Burke equation with the growth exponent m = 2. The analysis of topology further indicates that normal grain growth can be simulated fairly well by the present CA model. The vanishing of grains with different number of sides is discussed in the simulation

Grain growth kinetics of textured-BaTiO3 ceramics

Indian Academy of Sciences (India)

Administrator

3Department of Physics and Materials Science, City University of Hong Kong, Hong Kong ... Abstract. Textured BaTiO3 (BT) ceramics were fabricated by templated grain growth method. Effects of ... approaches to improve electrical properties of lead-free ceramics. ... modification methods to enhance the piezoelectric pro-.

Grain Growth and Precipitation Behavior of Iridium Alloy DOP-26 During Long Term Aging

Energy Technology Data Exchange (ETDEWEB)

Pierce, Dean T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Muralidharan, Govindarajan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Fox, Ethan E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cox, Victoria A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Geer, Tom [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-05-01

The influence of long term aging on grain growth and precipitate sizes and spatial distribution in iridium alloy DOP-26 was studied. Samples of DOP-26 were fabricated using the new process, recrystallized for 1 hour (h) at 1375 C, then aged at either 1300, 1400, or 1500 C for times ranging from 50 to 10,000 h. Grain size measurements (vertical and horizontal mean linear intercept and horizontal and vertical projection) and analyses of iridium-thorium precipitates (size and spacing) were made on the longitudinal, transverse, and rolling surfaces of the as-recrystallized and aged specimens from which the two-dimensional spatial distribution and mean sizes of the precipitates were obtained. The results obtained from this study are intended to provide input to grain growth models.

The effect of some growth regulators on enzyme systems in irradiated barley grain using disinfestation doses

International Nuclear Information System (INIS)

Bachman, S.

1973-01-01

Disinfestation doses of 20 to 100 krad may cause changes in the biological systems of barley grain and, therefore, may influence undesirably the technological quality of malted grain. The effect of some growth regulators on irradiated grain has been investigated. The experiments have been carried out on brewery barley var. Visa Breuns. Following growth-regulators were used: gibberellic acid (Polish preparation ''Gibrescol''), kinetin (6-furfurylo-aminopurin), CCC (2-chloroethyl trimethyl ammonium chloride), and betaine hydrochloride. By treating the irradiated barley with solutions of growth regulators it was possible to diminish the loss of enzyme activity. A ''regenerating'' effect of growth substances, mainly gibberellic acid and betain hydrochloride in 10 -4 M solutions, was observed. Amylolytic activity decreased immediately after irradiation but in samples treated with growth regulators it was higher than in those without regulators. The results may have a practical importance since gibberellic acid has just been introduced into the brewery industry. (F.J.)

A highly efficient 3D level-set grain growth algorithm tailored for ccNUMA architecture

Science.gov (United States)

Mießen, C.; Velinov, N.; Gottstein, G.; Barrales-Mora, L. A.

2017-12-01

A highly efficient simulation model for 2D and 3D grain growth was developed based on the level-set method. The model introduces modern computational concepts to achieve excellent performance on parallel computer architectures. Strong scalability was measured on cache-coherent non-uniform memory access (ccNUMA) architectures. To achieve this, the proposed approach considers the application of local level-set functions at the grain level. Ideal and non-ideal grain growth was simulated in 3D with the objective to study the evolution of statistical representative volume elements in polycrystals. In addition, microstructure evolution in an anisotropic magnetic material affected by an external magnetic field was simulated.

Anomalous grain growth in nanocrystalline Fe73.5Cu1Nb3Su13.5B9 alloys

DEFF Research Database (Denmark)

Jiang, Jianzhong

1997-01-01

The grain growth of the FeSi phase during the crystallization process of the amorphous Fe73.5Cu1Nb3Si13.5B9 alloy was studied using transmission electron microscopy and x-ray diffractometry. An anomalous grain growth behaviour of the FeSi phase in the samples annealed in temperature range from 743...... to 823 K for one hour was observed, i.e. the grain size of the FeSi phase slightly decreases when the annealing temperature increases from 743 K ot 823 K. The mechanism of the anomalous grain growth may be due to the different nucleation and volume diffusion rates in the samples anneales at low and high...

Three-dimensional investigation of grain orientation effects on void growth in commercially pure titanium

International Nuclear Information System (INIS)

Pushkareva, Marina; Adrien, Jérôme; Maire, Eric; Segurado, Javier; Llorca, Javier; Weck, Arnaud

2016-01-01

The fracture process of commercially pure titanium was visualized in model materials containing artificial holes. These model materials were fabricated using a femtosecond laser coupled with a diffusion bonding technique to obtain voids in the interior of titanium samples. Changes in void dimensions during in-situ straining were recorded in three dimensions using x-ray computed tomography. Void growth obtained experimentally was compared with the Rice and Tracey model which predicted well the average void growth. A large scatter in void growth data was explained by differences in grain orientation which was confirmed by crystal plasticity simulations. It was also shown that grain orientation has a stronger effect on void growth than intervoid spacing and material strength. Intervoid spacing, however, appears to control whether the intervoid ligament failure is ductile or brittle.

Three-dimensional investigation of grain orientation effects on void growth in commercially pure titanium

Energy Technology Data Exchange (ETDEWEB)

Pushkareva, Marina [Department of Mechanical Engineering, University of Ottawa, 150 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 (Canada); Adrien, Jérôme; Maire, Eric [Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, 7 Avenue Jean Capelle, F-69621 Villeurbanne (France); Segurado, Javier; Llorca, Javier [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science, Polytechnic University of Madrid, E. T. S. de Ingenieros de Caminos, 28040 Madrid (Spain); Weck, Arnaud, E-mail: aweck@uottawa.ca [Department of Mechanical Engineering, University of Ottawa, 150 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 (Canada); IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 (Canada); Centre for Research in Photonics at the University of Ottawa, 800 King Edward Ave., Ottawa, ON, Canada K1N 6N5 (Canada)

2016-08-01

The fracture process of commercially pure titanium was visualized in model materials containing artificial holes. These model materials were fabricated using a femtosecond laser coupled with a diffusion bonding technique to obtain voids in the interior of titanium samples. Changes in void dimensions during in-situ straining were recorded in three dimensions using x-ray computed tomography. Void growth obtained experimentally was compared with the Rice and Tracey model which predicted well the average void growth. A large scatter in void growth data was explained by differences in grain orientation which was confirmed by crystal plasticity simulations. It was also shown that grain orientation has a stronger effect on void growth than intervoid spacing and material strength. Intervoid spacing, however, appears to control whether the intervoid ligament failure is ductile or brittle.

Grain growth kinetics of ringwoodite and majorite garnet mixtures and implications for the rheology of the transition zone

Science.gov (United States)

Ezad, I.; Dobson, D. P.; Brodholt, J. P.; Thomson, A.; Hunt, S.

2017-12-01

The grain size of the transition zone is a poorly known but important geophysical parameter. Among others, the grain size may control the rheology, seismic attenuation and radiative thermal conductivity of the mantle. However, the grain size of the transition zone minerals ringwoodite (Mg,Fe)2SiO4 and majorite garnet MgSiO3 under appropriate zone conditions is currently unknown and there are very few experiments with which to constrain it. In order to determine the grain size of the transition zone, the grain growth kinetics must be determined for a range of mantle compositions. We have, therefore, experimentally determined the grain growth kinetics of the lowermost transition zone minerals through multi anvil experiments at University College London (UCL). This is achieved through a comprehensive set of time series experiments at pressures of 21 GPa and temperatures relevant to the transition zone. We have also determined the effect of varying water content, oxygen fugacity, iron content and aluminium content also discussed by Dobson and Mariani., (2014). Our initial grain growth experiments conducted at 1200°C and 1400°C at 18 GPa show extremely slow grain growth kinetics; time series experiments extended to 105.8 seconds are unable to produce grains larger than 100 nm. This suggests that fine-grained material at the base of the transition zone will persist on geological timescales. Such small grains size suggests that diffusion creep might be the dominant deformation mechanism in this region. Reference: Dobson, D.P., Mariani, E., 2014. The kinetics of the reaction of majorite plus ferropericlase to ringwoodite: Implications for mantle upwellings crossing the 660 km discontinuity. Earth Planet. Sci. Lett. 408, 110-118. doi:10.1016/j.epsl.2014.10.009

Determination of Sintered (Th,U)O2 Pellet at the Grain Growth Step

International Nuclear Information System (INIS)

Indrati-Y, Tundjung; Pristi-Hartati, Murdani; Ari-Handayani; Ginting, Aslina Br

2000-01-01

The determination of sintered (Th,U)O 2 pellet at the grain growth stephave been done by dilatometer and Scanning Electron Microscope (SEM). Thecalculation method based on the densification curve and quantitativemetallurgy. The green pellet be produced by single action compaction. Itspellet was heated on the dilatometer with heating rate 11 o C/minute and inthe argon atmosphere, 2 liters/hour. The activation energy at thedensification step can be calculated by densification curve only, but theactivation energy at the grain growth step can be calculated by densificationcurve or quantitative metallurgy. The capability of the dilatometer can beoperated until 1200 o C, so the densification curve based on the experiencecan be used to calculate activation energy at the densification step, 4.492kcal/mole. The activation energy at the grain growth step, which is 25.277kcal/mole, can be predicted by trial and error on n value. That activationenergy is almost the same with activation energy that based on thequantitative metallurgy method 25.042 kcal/mole. All of the activation energyfor the (Th,U)O 2 pellet sintering process is 29.769 kcal/mole. (author)

Investigation of the instability and low water kefir grain growth during an industrial water kefir fermentation process.

Science.gov (United States)

Laureys, David; Van Jean, Amandine; Dumont, Jean; De Vuyst, Luc

2017-04-01

A poorly performing industrial water kefir production process consisting of a first fermentation process, a rest period at low temperature, and a second fermentation process was characterized to elucidate the causes of its low water kefir grain growth and instability. The frozen-stored water kefir grain inoculum was thawed and reactivated during three consecutive prefermentations before the water kefir production process was started. Freezing and thawing damaged the water kefir grains irreversibly, as their structure did not restore during the prefermentations nor the production process. The viable counts of the lactic acid bacteria and yeasts on the water kefir grains and in the liquors were as expected, whereas those of the acetic acid bacteria were high, due to the aerobic fermentation conditions. Nevertheless, the fermentations progressed slowly, which was caused by excessive substrate concentrations resulting in a high osmotic stress. Lactobacillus nagelii, Lactobacillus paracasei, Lactobacillus hilgardii, Leuconostoc mesenteroides, Bifidobacterium aquikefiri, Gluconobacter roseus/oxydans, Gluconobacter cerinus, Saccharomyces cerevisiae, and Zygotorulaspora florentina were the most prevalent microorganisms. Lb. hilgardii, the microorganism thought to be responsible for water kefir grain growth, was not found culture-dependently, which could explain the low water kefir grain growth of this industrial process.

Numerical and Experimental Investigation of the Influence of Growth Restriction on Grain Size in Binary Cu Alloys

Directory of Open Access Journals (Sweden)

Andreas Cziegler

2017-09-01

Full Text Available Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several alloying elements of the Cu system was examined. To predict grain size depending on the growth restriction factor Q, grain size modelling was performed. The results obtained by the grain size model were compared to variations in the grain size of binary Cu alloys with increasing solute content under defined cooling conditions of the TP-1 grain refiner test of the Aluminium Association©. It was found that the experimental results differed significantly from the predicted grain size values for several alloying elements. A decreasing grain size with increasing alloy concentration was observed independently of the growth restriction potency of the alloying elements. Furthermore, excessive grain coarsening was found for several solutes beyond a transition point. It is assumed that contradictory variations in grain size result from a change in the nucleating particle density of the melt. Significant decreases in grain size are supposed to be due to the in-situ formation of potent nucleation sites. Excessive grain coarsening with increasing solute content may occur due to the removal of nucleating particles. The model shows that the difference in the actual number of particles before and beyond the transition point must be in the range of several orders of magnitude.

Watching the growth of bulk grains during recrystallization of deformed metals

DEFF Research Database (Denmark)

Schmidt, Søren; Fæster Nielsen, Søren; Gundlach, C.

2004-01-01

, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical...

Grain growth behavior and high-temperature high-strain-rate tensile ductility of iridium alloy DOP-26

International Nuclear Information System (INIS)

McKamey, C.G.; Gubbi, A.N.; Lin, Y.; Cohron, J.W.; Lee, E.H.; George, E.P.

1998-04-01

This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the new-process iridium-based DOP-26 alloy used for the Cassini space mission. This alloy was developed at Oak Ridge National Laboratory (ORNL) in the early 1980's and is currently used by NASA for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. Included within this report are data generated on grain growth in vacuum or low-pressure oxygen environments; a comparison of grain growth in vacuum of the clad vent set cup material with sheet material; effect of grain size, test temperature, and oxygen exposure on high-temperature high-strain-rate tensile ductility; and grain growth in vacuum and high-temperature high-strain-rate tensile ductility of welded DOP-26. The data for the new-process material is compared to available old-process data

Interaction Between Second-Phase Particle Dissolution and Abnormal Grain Growth in an Austenitic Stainless Steel

Directory of Open Access Journals (Sweden)

Dutra J.C.

2002-01-01

Full Text Available The continuing development of stainless steels has resulted in complex steel compositions with substantial amounts of alloying elements. The benefits of such additions invariably come attached to unavoidable disadvantages. One of the most critical item is the potential microstructural instability of the material. Alloying elements may be in a supersaturated solid solution, in which the precipitation of carbides, nitrides, borides and intermetallic phases occurs in a wide range of temperatures. In order to dissolve the mentioned precipitates, solution annealing is commonly performed. However, at the temperature range in which this treatment is carried out, the onset of abnormal grain growth can occur. The interaction between the dissolution of these second-phase particles and the occurrence of abnormal grain growth is investigated in this work. This study also shows that the thermodynamics and the kinetics of dissolution of precipitates may be used to predict whether abnormal grain growth takes place.

The coupled kinetics of grain growth and fission product behavior in nuclear fuel under degraded-core accident conditions

International Nuclear Information System (INIS)

Rest, J.

1985-01-01

The theoretical FASTGRASS-VFP model has been used in the interpretation of fission gas, iodine, and cesium release from (1) irradiated high-burnup LWR fuel in a flowing steam atmosphere during high-temperature, in-cell heating tests (performed at Oak Ridge National Laboratory) and (2) trace-irratiated LWR fuel during severe-fuel-damage (SFD) tests (performed in the PBF reactor in Idaho). A theory of grain boundary sweeping of gas bubbles has been included within the FASTGRASS-VFP formalism. This theory considers the interaction between the moving grain boundary and two distinct size classes of bubbles, those on grain faces and on grain edges, and provides a means of determining whether gas bubbles are caught up and moved along by a moving grain boundary or whether the grain boundary is only temporarily retarded by the bubbles and then breaks away. In addition, as FASTGRASS-VFP provides for a mechanistic calculation of intra- and intergranular fission product behavior, the coupled calculation between fission gas behavior and grain growth is kinetically comprehensive. Results of the analyses demonstrate that intragranular fission product behavior during both types of tests can be interpreted in terms of a grain-growth/grain-boundary-sweeping mechanism that enhances the flow of fission products from within the grains to the grain boundaries. The effect of fuel oxidation by steam on fission product and grain growth behavior is also considered. The FASTGRASS-VFP predictions, measured release rates from the above tests, and previously published release rates are compared and differences between fission product behavior in trace-irradiated and in high-burnup fuel are highlighted. (orig.)

Multiple oxide content media for columnar grain growth in L10 FePt thin films

International Nuclear Information System (INIS)

Ho, Hoan; Yang, En; Laughlin, David E.; Zhu, Jian-Gang

2013-01-01

An approach to enhance the height-to-diameter ratio of FePt grains in heat-assisted magnetic recording media is proposed. The FePt-SiO x thin films are deposited with a decrease of the SiO x percentage along the film growth direction. When bi-layer and tri-layer media are sputtered at 410 °C, we observe discontinuities in the FePt grains at interfaces between layers, which lead to poor epitaxial growth. Due to increased atomic diffusion, the bi-layer media sputtered at 450 °C is shown to (1) grow into continuous columnar grains with similar size as single-layer media but much higher aspect ratio, (2) have better L1 0 ordering and larger coercivity.

Austenite Grain Growth Behavior of AISI 4140 Alloy Steel

Directory of Open Access Journals (Sweden)

Lin Wang

2013-01-01

Full Text Available AISI 4140 alloy steel is widely applied in the manufacture of various parts such as gears, rams, and spindles due to its good performance of strength, toughness, and wear resistance. The former researches most focused on its deformation and recrystallization behaviors under high temperature. However, the evolution laws of austenite grain growth were rarely studied. This behavior also plays an important role in the mechanical properties of parts made of this steel. In this study, samples are heated to a certain temperature of 1073 K, 1173 K, 1273 K, and 1373 K at a heating rate of 5 K per second and hold for different times of 0 s, 120 s, 240 s, 360 s, and 480 s before being quenched with water. The experimental results suggest that the austenite grains enlarge with increasing temperature and holding time. A mathematical model and an application developed in Matlab environment are established on the basis of previous works and experimental results to predict austenite grains size in hot deformation processes. The predicted results are in good agreement with experimental results which indicates that the model and the application are reliable.

Effect of pre- and post-heading waterlogging on growth and grain yield of four millets

Directory of Open Access Journals (Sweden)

Asana Matsuura

2016-07-01

Full Text Available Seeds of Panicum miliaceum, Panicum sumatrense, Setaria glauca, and Setaria italica were raised in polyvinylchloride tubes filled with soil to determine interspecific differences in waterlogging tolerance and the effect of pre- and post-heading waterlogging on growth and grain yield. Four treatments were conducted including control (no-waterlogging stress during growth. Pre-heading waterlogging treatment was initiated 17 days after sowing to heading (TC. Post-heading waterlogging treatment was initiated heading till harvest (CT. Waterlogging treatment was initiated 17 days after sowing to harvesting (TT. The grain yield of P. miliaceum, S. glauca, and S. italica decreased 16, 18, and 4%, while that of P. sumatrense increased 210% under TT treatment and this showed P. sumatrense had most waterlogging tolerance. The grain yield was more affected under TC treatment in S. italica and P. miliaceum. However, there was not significant differences the grain yield between TC and CT treatment in P. sumatrense and S. glauca. Total dry weight, total root dry weight, number of crown root, and the proportion of lysigenous aerenchyma of P. sumatrense were significantly higher than those of other millets at harvesting. Plant growth rate, total root dry weight, number of crown root, and the proportion of lysigenous aerenchyma of P. sumatrense were significantly higher than those of other millets at heading. These results suggest that P. sumatrense exhibits waterlogging tolerance by enhancing root growth characterized by a high proportion of lysigenous aerenchyma in the crown root.

Effect of zirconium on grain growth and mechanical properties of a ball-milled nanocrystalline FeNi alloy

Energy Technology Data Exchange (ETDEWEB)

Kotan, Hasan, E-mail: hkotan@ncsu.edu [Department of Materials Science and Engineering, NC State University, 911 Partners Way, Room 3078, Raleigh, NC 27606-7907 (United States); Darling, Kris A. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005-5069 (United States); Saber, Mostafa; Koch, Carl C.; Scattergood, Ronald O. [Department of Materials Science and Engineering, NC State University, 911 Partners Way, Room 3078, Raleigh, NC 27606-7907 (United States)

2013-02-25

Highlights: Black-Right-Pointing-Pointer Pure Fe, Fe{sub 92}Ni{sub 8}, and Fe{sub 91}Ni{sub 8}Zr{sub 1} powders were hardened up to 10 GPa by ball milling. Black-Right-Pointing-Pointer Annealing of Fe and Fe{sub 92}Ni{sub 8} leads to reduced hardness and extensive grain growth. Black-Right-Pointing-Pointer The addition of Zr to Fe{sub 92}Ni{sub 8} increases its stability and strength by second phases. Black-Right-Pointing-Pointer The second phases are found to promote the stability of Fe{sub 91}Ni{sub 8}Zr{sub 1} by Zener pinning. Black-Right-Pointing-Pointer The Zr-containing precipitates contribute to the overall strength of the material. - Abstract: Grain growth of ball-milled pure Fe, Fe{sub 92}Ni{sub 8}, and Fe{sub 91}Ni{sub 8}Zr{sub 1} alloys has been studied using X-ray diffractometry (XRD), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). Mechanical properties with respect to compositional changes and annealing temperatures have been investigated using microhardness and shear punch tests. We found the rate of grain growth of the Fe{sub 91}Ni{sub 8}Zr{sub 1} alloy to be much less than that of pure Fe and the Fe{sub 92}Ni{sub 8} alloy at elevated temperatures. The microstructure of the ternary Fe{sub 91}Ni{sub 8}Zr{sub 1} alloy remains nanoscale up to 700 Degree-Sign C where only a few grains grow abnormally whereas annealing of pure iron and the Fe{sub 92}Ni{sub 8} alloy leads to extensive grain growth. The grain growth of the ternary alloy at high annealing temperatures is coupled with precipitation of Fe{sub 2}Zr. A fine dispersion of precipitated second phase is found to promote the microstructural stability at high annealing temperatures and to increase the hardness and ultimate shear strength of ternary Fe{sub 91}Ni{sub 8}Zr{sub 1} alloy drastically when the grain size is above nanoscale.

[Impacts of drought stress on the growth and development and grain yield of spring maize in Northeast China].

Science.gov (United States)

Ji, Rui-Peng; Che, Yu-Sheng; Zhu, Yong-Ning; Liang, Tao; Feng, Rui; Yu, Wen-Ying; Zhang, Yu-Shu

2012-11-01

Taking spring maize variety Danyu-39 as test object, an experiment was conducted in a large-scale agricultural water controlling experimental field to study the impacts of drought stress at three key growth stages, i. e. , 3-leaf-jointing, jointing-silking, and silking-milk ripe, on the growth and development and grain yield of spring maize in Northeast China. Two treatments were installed, including moderate drought stress (MS) and re-watering to suitable water (CK). Compared with CK, the MS at 3-leaf-jointing stage postponed the whole growth period of Danyu-39 by 13 d, and the plant height and leaf area at jointing stage were decreased by 29.8% and 41.2%, respectively. After re-watering, the plant height and grain yield recovered obviously, and the differences in ear characteristics and final yield were insignificant. The MS at jointing-silking stage shortened the whole growth period by 7 d, the plant height and leaf area at silking stage were decreased by 18.6% and 14.1%, respectively, the ear length, grain number per ear, ear dry mass, and grain mass per ear decreased by 6.9%, 19.1%, 28.1%, and 29.4%, respectively, and the blank stem rate increased by 13.3%. When the maize suffered from moderate drought stress at silking-milk ripe stage, the whole growth period was shortened by 15 d, the plant height and leaf area at milk ripe stage were decreased by 2.3% and 37.3%, respectively, the ear length, grain number per ear, ear dry mass, and grain mass per ear decreased by 9.2%, 24.1%, 30.8%, and 27.9%, respectively, and the blank stem rate increased by 24.5%. After re-watering at the latter two stages, the recovery of plant height was little, and the grain yield decreased significantly.

Niobium effects on the austenitic grain growth and hardenability of steels for mechanical construction

International Nuclear Information System (INIS)

Vieira, R.R.; Arruda Camargo, L.M. de; Oliveira Junior, G.G. de; Dias Filho, A.G.C.

1983-01-01

The austenitic grain growth and hardenability of SAE 86XX and 5120 steels modified with 0,001 to 0,20 per-cent niobium content were studied when submitted to case hardening and quenching heat treatments. The results show that niobium controlS the austenite grain size better than molybdenum up to 950 0 C austenitization temperature. The hardenability, evaluated by the Jominy test which the modified SAE 8640 steels, is more strongly inflencied by the grain refining resulting from niobium addition than by any other supposed effect. (Author) [pt

Effects of seed geometry on the crystal growth and the magnetic properties of single grain REBCO bulk superconductors

Energy Technology Data Exchange (ETDEWEB)

Lee, Hwi Joo; Lee, Hee Gyoun [Korea Polytechnic University, Siheung (Korea, Republic of); Park, Soon Dong; Jun, Bung Hyack; Kim, Chan Joong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-09-15

This study presents that the orientation and the geometry of seed affect on the growth behavior of melt processed single grain REBCO bulk superconductor and its magnetic properties. The effects of seed geometry have been investigated for thin 30mm x 30mm rectangular powder compacts. Single grain REBCO bulk superconductors have been grown successfully by a top seed melt growth method for 8-mm thick vertical thin REBCO slab. Asymmetric structures have been developed at the front surface and at the rear surface of the specimen. Higher magnetic properties have been obtained for the specimen that c-axis is normal to the specimen surface. The relationships between microstructure, grain growth and magnetic properties have been discussed.

The free growth criterion for grain initiation in TiB 2 inoculated γ-titanium aluminide based alloys

Science.gov (United States)

Gosslar, D.; Günther, R.

2014-02-01

γ-titanium aluminide (γ-TiAl) based alloys enable for the design of light-weight and high-temperature resistant engine components. This work centers on a numerical study of the condition for grain initiation during solidification of TiB2 inoculated γ-TiAl based alloys. Grain initiation is treated according to the so-called free growth criterion. This means that the free growth barrier for grain initiation is determined by the maximum interfacial mean curvature between a nucleus and the melt. The strategy presented in this paper relies on iteratively increasing the volume of a nucleus, which partially wets a hexagonal TiB2 crystal, minimizing the interfacial energy and calculating the corresponding interfacial curvature. The hereby obtained maximum curvature yields a scaling relation between the size of TiB2 crystals and the free growth barrier. Comparison to a prototypical TiB2 crystal in an as cast γ-TiAl based alloy allowed then to predict the free growth barrier prevailing under experimental conditions. The validity of the free growth criterion is discussed by an interfacial energy criterion.

Finite-Element Thermal Analysis and Grain Growth Behavior of HAZ on Argon Tungsten-Arc Welding of 443 Stainless Steel

Directory of Open Access Journals (Sweden)

Yichen Wang

2016-03-01

Full Text Available This paper presents a numerical and infrared experimental study of thermal and grain growth behavior during argon tungsten arc welding of 443 stainless steel. A 3D finite element model was proposed to simulate the welding process. The simulations were carried out via the Ansys Parametric Design Language (APDL available in the finite-element code, ANSYS. To validate the simulation accuracy, a series of experiments using a fully-automated welding process was conducted. The results of the numerical analysis show that the simulation weld bead size and the experiment results have good agreement. The grain growth in the heat-affected zone of 443 stainless steel is influenced via three factors: (1 the thermal cycle experienced; (2 grain boundary migration; and (3 particle precipitation. Grain boundary migration is the main factor. The modified coefficient k of the grain growth index is calculated. The value is 1.16. Moreover, the microhardness of the weld bead softened slightly compared to the base metal.

Effect of continuous change of sintering atmosphere on the grain growth of Cr-doped UO2 pellets

International Nuclear Information System (INIS)

Yang, Jae Ho; Nam, Ik Hui; Kim, Jong Hun; Rhee, Young Woo; Kim, Dong Joo; Kim, Keon Sik; Song, Kun Woo

2010-01-01

Cr-doped UO 2 pellet is one of the promising candidates for the high burn-up fuel in commercial LWRs. Major nuclear fuel vendors of such as AREVA or Westinghouse initiated the development of Cr-doped or Cr-containing additives doped UO 2 pellets since at the mid of 90's. Now, qualification programs are on-going to provide these pellets commercially. The main characteristics of the Cr-doped pellets are large-grain and visco-plasticity. Large grain pellet can reduce the corrosive fission gas release at high burn up. Viscoplastic soft pellets can lower the pressure to a cladding caused by a thermal expansion of a pellet at an elevated temperature during transient operations. Those advantages can provide room for additional power uprates and high burnup limits. Especially, PCI resistance improvement can be achieved by enlarging the pellet grain size and enhancing the fuel deformation at an elevated temperature. In this paper, to study the effect of oxygen partial pressure on grain growth in Cr-doped UO 2 pellets, Cr- doped UO 2 samples have been sintered with and without a step-wise change of sintering atmospheres. An introduction of a step-wise variation of oxygen partial pressure during the sintering enhances the grain growth of UO 2 pellets greatly. This step-wise sintering effect has been explained in terms of a continuous increase of Cr concentration along the grain boundary. The observed grain growth behavior under step-wisely changed sintering atmospheres demonstrates the possibility of reducing the amount of Cr 2 O 3 to minimum via control of oxygen partial pressure while keeping the large grain size

Effects of seed orientation on the growth behavior of single grain REBCO bulk superconductors

Energy Technology Data Exchange (ETDEWEB)

Lee, Hee Gyoun [Korea Polytechnic University, Siheung (Korea, Republic of)

2017-06-15

This study presents a simple method to control the seed orientation which leads to the various growth characteristics of a single grain REBCO (RE: rare-earth elements) bulk superconductors. Seed orientation was varied systematically from c-axis to a-axis with every 30 degree rotation around b-axis. Orientations of a REBCO single grain was successfully controlled by placing the seed with various angles on the prismatic indent prepared on the surface of REBCO powder compacts. Growth pattern was changed from cubic to rectangular when the seed orientation normal to compact surface was varied from c-axis to a-axis. Macroscopic shape change has been explained by the variation of the wetting angle of un-reacted melt depending on the interface energy between YBa2Cu3O7-y (Y123) grain and melt. Higher magnetic levitation force was obtained for the specimen prepared using tilted seed with an angle of 30 degree rotation around b-axis.

Growth of single crystalline seeds into polycrystalline strontium titanate: Anisotropy of the mobility, intrinsic drag effects and kinetic shape of grain boundaries

International Nuclear Information System (INIS)

Rheinheimer, Wolfgang; Bäurer, Michael; Handwerker, Carol A.; Blendell, John E.; Hoffmann, Michael J.

2015-01-01

We present a suite of measurements and combined analyses of grain growth in SrTiO 3 for oriented single crystals into polycrystals. The growth distance and standard deviation and the microstructure evolution along the single crystal–matrix interface are used to locally characterize the change in migration behavior as a function of temperature, time and interface orientation. The relative grain boundary mobility was determined between 1250 °C and 1600 °C for four crystallographic orientations {1 0 0}, {1 1 0}, {1 1 1} and {3 1 0}. An absolute mobility of these orientations is estimated. Under fast growth conditions the morphology of single crystals shows macroscopic stepping with parts of the interface rotating to low mobility orientations. This effect represents a kinetic influence on the grain boundary morphology. The results also indicate dragging effects on microstructure coarsening, which indicate the existence of a critical driving force for grain growth. This critical driving force seems to be related to an ‘intrinsic’ interface drag similar to the solute drag, but based on intrinsic defects. At 1460 °C the growth of single crystals was significantly faster than expected from the mobility of the polycrystal and was identified as exaggerated grain growth. The findings give new insights into the recently published grain growth anomaly of strontium titanate, leading to a hypothesis based on the temperature dependent relative mobility of {1 0 0} oriented grain boundaries

B2 Grain Growth Behavior of a Ti-22Al-25Nb Alloy Fabricated by Hot Pressing Sintering

Science.gov (United States)

Jia, Jianbo; Liu, Wenchao; Xu, Yan; Chen, Chen; Yang, Yue; Luo, Junting; Zhang, Kaifeng

2018-05-01

Grain growth behavior of a powder metallurgy (P/M) Ti-22Al-25Nb alloy was investigated by applying a series of isothermal treatment tests over a wide range of temperatures and holding times. An isothermal treatment scheme was conducted in the B2 phase region (1070-1110 °C) and α 2 + B2 phase region (1010-1050 °C) at holding times of 10, 30 min, 1, 2, and 3 h, respectively. The effects of temperature and holding time on the microstructure evolution and microhardness of the P/M Ti-22Al-25Nb alloy at elevated temperatures were evaluated using optical microscope, scanning electron microscope, x-ray diffraction, and Vickers hardness test techniques. The results revealed that the alloy's treated microstructure was closely linked to temperature and holding time, respectively. The change law of B2 grain growth with holding time and temperature can be well interpreted by the Beck equation and Hillert equation, respectively. The B2 grain growth exponent n and activation energy Q were acquired based on experimental data in the α 2 + B2 and B2 phase regions. In addition, the grain growth contour map for the P/M Ti-22Al-25Nb alloy was constructed to depict variations in B2 grain size based on holding time and temperature.

Effect of Fungicide Applications on Grain Sorghum (Sorghum bicolor L. Growth and Yield

Directory of Open Access Journals (Sweden)

Dan D. Fromme

2017-01-01

Full Text Available Field studies were conducted in the upper Texas Gulf Coast and in central Louisiana during the 2013 through 2015 growing seasons to evaluate the effects of fungicides on grain sorghum growth and development when disease pressure was low or nonexistent. Azoxystrobin and flutriafol at 1.0 L/ha and pyraclostrobin at 0.78 L/ha were applied to the plants of two grain sorghum hybrids (DKS 54-00, DKS 53-67 at 25% bloom and compared with the nontreated check for leaf chlorophyll content, leaf temperature, and plant lodging during the growing season as well as grain mold, test weight, yield, and nitrogen and protein content of the harvested grain. The application of a fungicide had no effect on any of the variables tested with grain sorghum hybrid responses noted. DKS 53-67 produced higher yield, greater test weight, higher percent protein, and N than DKS 54-00. Results of this study indicate that the application of a fungicide when little or no disease is present does not promote overall plant health or increase yield.

Effect of sintering condition on the grain growth of Cr{sub 2}O{sub 3} doped UO{sub 2} pellets

Energy Technology Data Exchange (ETDEWEB)

Oh, Jang Soo; Kim, Keon Sik; Kim, Dong Joo; Kim, Jong Hun; Yang, Jae Ho [KAERI, Daejeon (Korea, Republic of)

2016-05-15

In this paper, Cr{sub 2}O{sub 3} doped UO{sub 2} pellets were fabricated by two-step sintering process. The grain growth of pellet is related to dwell time in a hydrogen atmosphere during sintering process. A large grain pellet can minimize fission gas release and deform easily at an elevated temperature. So, the recent development of nuclear fuel pellet materials is mainly focused on the large grain pellets. The various methods of fabrication processes for large grain UO{sub 2} pellets have been investigated extensively. Those parameters include the additives, sintering temperature, sintering time, sintering atmosphere, and so on. Cr-doped UO{sub 2} pellet is one of the promising candidates for PCI remedy. It was shown that the grain size and softness of UO{sub 2} pellets could be enhanced by doping Cr or Cr compound in UO{sub 2}. Various in-pile test results revealed that the PCI properties were enhanced considerably [4]. In the sintering process of Cr-doped UO{sub 2} pellet, it was known that tight adjusting of sintering atmosphere is most important to achieve large grain pellet. The relevant research revealed that the doped Cr{sub 2}O{sub 3} became liquid phase in optimized oxygen potential and that liquid phase promoted the grain growth. Recently, KAERI has shown that grain size of Cr-doped UO{sub 2} pellet could be more enlarged by adjusting process parameters. In this paper, we introduced a sintering process which can form a liquid phase for a large grain growth in Cr{sub 2}O{sub 3} doped UO{sub 2} pellet. The study on the effect of dwell time in H{sub 2} atmosphere during sintering process on the grain structure of sintered pellet is also a part of this work. In order to obtain large grain in pellet, it is important to increase amount of Cr that can form a liquid phase for grain growth by increasing dwell time in a hydrogen atmosphere during sintering process.

Modeling Nucleation and Grain Growth in the Solar Nebula: Initial Progress Report

Science.gov (United States)

Nuth, Joseph A.; Paquette, J. A.; Ferguson, F. T.

2010-01-01

The primitive solar nebula was a violent and chaotic environment where high energy collisions, lightning, shocks and magnetic re-connection events rapidly vaporized some fraction of nebular dust, melted larger particles while leaving the largest grains virtually undisturbed. At the same time, some tiny grains containing very easily disturbed noble gas signatures (e.g., small, pre-solar graphite or SiC particles) never experienced this violence, yet can be found directly adjacent to much larger meteoritic components (chondrules or CAIs) that did. Additional components in the matrix of the most primitive carbonaceous chondrites and in some chondritic porous interplanetary dust particles include tiny nebular condensates, aggregates of condensates and partially annealed aggregates. Grains formed in violent transient events in the solar nebula did not come to equilibrium with their surroundings. To understand the formation and textures of these materials as well as their nebular abundances we must rely on Nucleation Theory and kinetic models of grain growth, coagulation and annealing. Such models have been very uncertain in the past: we will discuss the steps we are taking to increase their reliability.

A parallelized three-dimensional cellular automaton model for grain growth during additive manufacturing

Science.gov (United States)

Lian, Yanping; Lin, Stephen; Yan, Wentao; Liu, Wing Kam; Wagner, Gregory J.

2018-05-01

In this paper, a parallelized 3D cellular automaton computational model is developed to predict grain morphology for solidification of metal during the additive manufacturing process. Solidification phenomena are characterized by highly localized events, such as the nucleation and growth of multiple grains. As a result, parallelization requires careful treatment of load balancing between processors as well as interprocess communication in order to maintain a high parallel efficiency. We give a detailed summary of the formulation of the model, as well as a description of the communication strategies implemented to ensure parallel efficiency. Scaling tests on a representative problem with about half a billion cells demonstrate parallel efficiency of more than 80% on 8 processors and around 50% on 64; loss of efficiency is attributable to load imbalance due to near-surface grain nucleation in this test problem. The model is further demonstrated through an additive manufacturing simulation with resulting grain structures showing reasonable agreement with those observed in experiments.

A parallelized three-dimensional cellular automaton model for grain growth during additive manufacturing

Science.gov (United States)

Lian, Yanping; Lin, Stephen; Yan, Wentao; Liu, Wing Kam; Wagner, Gregory J.

2018-01-01

In this paper, a parallelized 3D cellular automaton computational model is developed to predict grain morphology for solidification of metal during the additive manufacturing process. Solidification phenomena are characterized by highly localized events, such as the nucleation and growth of multiple grains. As a result, parallelization requires careful treatment of load balancing between processors as well as interprocess communication in order to maintain a high parallel efficiency. We give a detailed summary of the formulation of the model, as well as a description of the communication strategies implemented to ensure parallel efficiency. Scaling tests on a representative problem with about half a billion cells demonstrate parallel efficiency of more than 80% on 8 processors and around 50% on 64; loss of efficiency is attributable to load imbalance due to near-surface grain nucleation in this test problem. The model is further demonstrated through an additive manufacturing simulation with resulting grain structures showing reasonable agreement with those observed in experiments.

Multiseeding with (100)/(100) Grain Junctions in Top Seeded Melt Growth Processed YBCO Superconductors

Energy Technology Data Exchange (ETDEWEB)

Kim, C.J.; Gee, Y.A.; Hong, G.W. [Korea Atomic Energy Research Institute, Taejon (Korea); Kim, H.J.; Joo, J.H. [Sungkyunkwan University, Suwon (Korea); Han, S.C.; Han, Y.H.; Sung, T.H.; Kim, S.J. [Korea Electric Power Research Institute, Taejon (Korea)

2000-06-01

Multiseeding with (100)/(100) grain junctions of top-seeded melt growth (TSMG) processed YBCO superconductors was studied. Multiple seeding shortened the processing time for the fabrication of TSMG-processed YBCO superconductors. The relationship among the number of seeds, the levitation forces and the trapped magnetic fields of the TSMG-processed YBCO samples is reported. The characteristic of the (100)/(100) grain junction is discussed in terms of a wetting angle of a melt. (author). 25 refs., 7 figs.

The evolution of grain mantles and silicate dust growth at high redshift

Science.gov (United States)

Ceccarelli, Cecilia; Viti, Serena; Balucani, Nadia; Taquet, Vianney

2018-05-01

In dense molecular clouds, interstellar grains are covered by mantles of iced molecules. The formation of the grain mantles has two important consequences: it removes species from the gas phase and promotes the synthesis of new molecules on the grain surfaces. The composition of the mantle is a strong function of the environment that the cloud belongs to. Therefore, clouds in high-zeta galaxies, where conditions - like temperature, metallicity, and cosmic ray flux - are different from those in the Milky Way, will have different grain mantles. In the last years, several authors have suggested that silicate grains might grow by accretion of silicon-bearing species on smaller seeds. This would occur simultaneously with the formation of the iced mantles and be greatly affected by its composition as a function of time. In this work, we present a numerical study of the grain mantle formation in high-zeta galaxies, and we quantitatively address the possibility of silicate growth. We find that the mantle thickness decreases with increasing redshift, from about 120 to 20 layers for z varying from 0 to 8. Furthermore, the mantle composition is also a strong function of the cloud redshift, with the relative importance of CO, CO2, ammonia, methane, and methanol highly varying with z. Finally, being Si-bearing species always a very minor component of the mantle, the formation of silicates in molecular clouds is practically impossible.

Influence of intermediate annealing on abnormal Goss grain growth in the rolled columnar-grained Fe-Ga-Al alloys

International Nuclear Information System (INIS)

Liu, Yangyang; Li, Jiheng; Gao, Xuexu

2017-01-01

Highlights: • Texture of primary IA sample was dominated by γ-fiber with a peak at {1 1 1}<1 1 0>. • Texture of primary CR sample was dominated by {1 1 3}<1 1 4> texture. • Inhomogeneous microstructure was significantly improved in primary IA sample. • Strong Goss texture was obtained in final IA sample without surface energy control. - Abstract: Magnetostrictive Fe 82 Ga 4.5 Al 13.5 sheets with 0.1 at% NbC were prepared from directional solidified alloys with <0 0 1> preferred orientation. The slabs were hot rolled at 650 °C and warm rolled at 500 °C. Then some warm-rolled sheets were annealed intermediately at 850 °C for 5 min but the others not. After that, all the sheets were cold rolled to a final thickness of ∼0.3 mm. The microstructures, the textures and the distributions of second phase particles in the primary recrystallized samples were investigated. With intermediate annealing, the inhomogeneous microstructure was improved remarkably and strong Goss ({1 1 0}<0 0 1>) and γ-fiber (<1 1 1>//normal direction [ND]) textures were produced in the primary recrystallized samples. But, an evident disadvantage in size and quantity was observed for Goss grains in the primary recrystallized sample without intermediate annealing. After a final annealing, the final textures and magnetostrictions of samples with and without intermediate annealing were characterized. For samples without intermediate annealing, abnormal growth of {1 1 3} grains occurred and deteriorated the magnetostriction. In contrast, abnormal Goss grain growth occurred completely in samples with intermediate annealing and led to saturation magnetostriction as high as 156 ppm.

Influence of intermediate annealing on abnormal Goss grain growth in the rolled columnar-grained Fe-Ga-Al alloys

Energy Technology Data Exchange (ETDEWEB)

Liu, Yangyang; Li, Jiheng; Gao, Xuexu, E-mail: gaox@skl.ustb.edu.cn

2017-08-01

Highlights: • Texture of primary IA sample was dominated by γ-fiber with a peak at {1 1 1}<1 1 0>. • Texture of primary CR sample was dominated by {1 1 3}<1 1 4> texture. • Inhomogeneous microstructure was significantly improved in primary IA sample. • Strong Goss texture was obtained in final IA sample without surface energy control. - Abstract: Magnetostrictive Fe{sub 82}Ga{sub 4.5}Al{sub 13.5} sheets with 0.1 at% NbC were prepared from directional solidified alloys with <0 0 1> preferred orientation. The slabs were hot rolled at 650 °C and warm rolled at 500 °C. Then some warm-rolled sheets were annealed intermediately at 850 °C for 5 min but the others not. After that, all the sheets were cold rolled to a final thickness of ∼0.3 mm. The microstructures, the textures and the distributions of second phase particles in the primary recrystallized samples were investigated. With intermediate annealing, the inhomogeneous microstructure was improved remarkably and strong Goss ({1 1 0}<0 0 1>) and γ-fiber (<1 1 1>//normal direction [ND]) textures were produced in the primary recrystallized samples. But, an evident disadvantage in size and quantity was observed for Goss grains in the primary recrystallized sample without intermediate annealing. After a final annealing, the final textures and magnetostrictions of samples with and without intermediate annealing were characterized. For samples without intermediate annealing, abnormal growth of {1 1 3} grains occurred and deteriorated the magnetostriction. In contrast, abnormal Goss grain growth occurred completely in samples with intermediate annealing and led to saturation magnetostriction as high as 156 ppm.

A model for strain hardening, recovery, recrystallization and grain growth with applications to forming processes of nickel base alloys

Energy Technology Data Exchange (ETDEWEB)

Riedel, Hermann, E-mail: hermann.riedel@iwm.fraunhofer.de [Fraunhofer Institute for Materials Mechanics, Wöhlerstr. 11, 79108 Freiburg (Germany); Svoboda, Jiri, E-mail: svobj@ipm.cz [Institute of Physics of Materials, Academy of Science of the Czech Republic, Zizkova 22, Brno (Czech Republic)

2016-05-17

An ensemble of n spherical grains is considered, each of which is characterized by its radius r{sub i} and by a hardening variable a{sub i}. The hardening variable obeys a Chaboche-type evolution equation with dynamic and static recovery. The grain growth law includes the usual contribution of the grain boundary energy, a term for the stored energy associated with the hardening variable, and the Zener pinning force exerted by particles on the migrating grain boundaries. New grains develop by recrystallization in grains whose stored energy density exceeds a critical value. The growth or shrinkage of the particles, which restrain grain boundary migration, obeys a thermodynamic/kinetic evolution equation. This set of first order differential equations for r{sub i}, a{sub i} and the particle radius is integrated numerically. Fictitious model parameters for a virtual nickel base alloy are used to demonstrate the properties and capabilities of the model. For a real nickel alloy, model parameters are adjusted using measured stress-strain curves, as well as recrystallized volume fractions and grain size distributions. Finally the model with adjusted parameters is applied to a forming process with complex temperature-strain rate histories.

Grain growth behavior of Cr dispersed UO{sub 2} pellets according to change of oxygen potential during the isothermal sintering

Energy Technology Data Exchange (ETDEWEB)

Oh, Jang Soo; Yang, Jae Ho; Kim, Dong Joo; Kim, Jong Hun; Nam, Ik Hui; Rhee, Young Woo; Kim, Keon Sik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2012-10-15

Recent development of advanced UO{sub 2} pellet materials for commercial reactors is mainly focused on the large grain pellet which can deform easily at an elevated temperature. Cr{sub 2}O{sub 3}-doped UO{sub 2} pellet is one of the promising candidates. To increase the grain size effectively, it is important to control the additive content and sintering atmosphere. Relevant research on the Cr{sub 2}O{sub 3} doped UO{sub 2} system revealed that the doped Cr{sub 2}O{sub 3} formed a liquid phase under optimized oxygen potential, and those liquid phases promoted the grain growth. Recent work also showed that step-wise variation of sintering atmosphere during the isothermal annealing step significantly increased the grain size of Cr{sub 2}O{sub 3} doped UO{sub 2} pellet. In this paper, we investigated effect of oxygen potential change at the beginning of isothermal sintering stage on the grain growth in metallic Cr dispersed UO{sub 2} pellets. The study on the milling effect of powder mixture on the grain growth is also a part of this work.

Manufacturing process to reduce large grain growth in zirconium alloys

International Nuclear Information System (INIS)

Rosecrans, P.M.

1987-01-01

A method is described of treating cold worked zirconium alloys to reduce large grain growth during thermal treatment above its recrystallization temperature. The method comprises heating the zirconium alloy at a temperature of about 1300 0 F. to 1350 0 F. for about 1 to 3 hours subsequent to cold working the zirconium alloy and prior to the thermal treatment at a temperature of between 1450 0 -1550 0 F., the thermal treatment temperature being above the recrystallization temperature

Grain Nucleation and Growth in Deformed NiTi Shape Memory Alloys: An In Situ TEM Study

Science.gov (United States)

Burow, J.; Frenzel, J.; Somsen, C.; Prokofiev, E.; Valiev, R.; Eggeler, G.

2017-12-01

The present study investigates the evolution of nanocrystalline (NC) and ultrafine-grained (UFG) microstructures in plastically deformed NiTi. Two deformed NiTi alloys were subjected to in situ annealing in a transmission electron microscope (TEM) at 400 and 550 °C: an amorphous material state produced by high-pressure torsion (HPT) and a mostly martensitic partly amorphous alloy produced by wire drawing. In situ annealing experiments were performed to characterize the microstructural evolution from the initial nonequilibrium states toward energetically more favorable microstructures. In general, the formation and evolution of nanocrystalline microstructures are governed by the nucleation of new grains and their subsequent growth. Austenite nuclei which form in HPT and wire-drawn microstructures have sizes close to 10 nm. Grain coarsening occurs in a sporadic, nonuniform manner and depends on the physical and chemical features of the local environment. The mobility of grain boundaries in NiTi is governed by the local interaction of each grain with its microstructural environment. Nanograin growth in thin TEM foils seems to follow similar kinetic laws to those in bulk microstructures. The present study demonstrates the strength of in situ TEM analysis and also highlights aspects which need to be considered when interpreting the results.

Grain growth kinetics and electrical properties of lanthanum modified lead zirconate titanate (9/65/35) based ferroelectric ceramics

International Nuclear Information System (INIS)

Roca, R. Alvarez; Guerrero, F.; Botero, E. R.; Garcia, D.; Eiras, J. A.; Guerra, J. D. S.

2009-01-01

The influence of the microstructural characteristics on the dielectric and electrical properties has been investigated for Nd 3+ doped lanthanum modified lead zirconate titanate ferroelectric ceramics, obtained by the conventional solid-state reaction method, by taking into account different sintering conditions. The grain growth mechanism has been investigated and a cubic-type grain growth law was observed for samples with grain size varying from 1.00 up to 2.35 μm. The porosity and grain size dependences of the phase transition parameters, such as the maximum dielectric permittivity and its corresponding temperature (ε m and T m , respectively) were also investigated. The ac conductivity analyses followed the universal Jonscher law. The behavior of the frequency exponent (s) was analyzed through the correlated barrier hopping model. Both ac and dc conductivity results have been correlated with the observed microstructural features

Mechanism of secondary recrystallization of Goss grains in grain-oriented electrical steel

Science.gov (United States)

Hayakawa, Yasuyuki

2017-12-01

Since its invention by Goss in 1934, grain-oriented (GO) electrical steel has been widely used as a core material in transformers. GO exhibits a grain size of over several millimeters attained by secondary recrystallization during high-temperature final batch annealing. In addition to the unusually large grain size, the crystal direction in the rolling direction is aligned with , which is the easy magnetization axis of α-iron. Secondary recrystallization is the phenomenon in which a certain very small number of {110} (Goss) grains grow selectively (about one in 106 primary grains) at the expense of many other primary recrystallized grains. The question of why the Goss orientation is exclusively selected during secondary recrystallization has long been a main research subject in this field. The general criterion for secondary recrystallization is a small and uniform primary grain size, which is achieved through the inhibition of normal grain growth by fine precipitates called inhibitors. This paper describes several conceivable mechanisms of secondary recrystallization of Goss grains mainly based on the selective growth model.

Why do interstellar grains exist

International Nuclear Information System (INIS)

Seab, C.G.; Hollenbach, D.J.; Mckee, C.F.; Tielens, A.G.G.M.

1986-01-01

There exists a discrepancy between calculated destruction rates of grains in the interstellar medium and postulated sources of new grains. This problem was examined by modelling the global life cycle of grains in the galaxy. The model includes: grain destruction due to supernovae shock waves; grain injection from cool stars, planetary nebulae, star formation, novae, and supernovae; grain growth by accretion in dark clouds; and a mixing scheme between phases of the interstellar medium. Grain growth in molecular clouds is considered as a mechanism or increasing the formation rate. To decrease the shock destruction rate, several new physical processes, such as partial vaporization effects in grain-grain collisions, breakdown of the small Larmor radius approximation for betatron acceleration, and relaxation of the steady-state shock assumption are included

Polymer-Coated Urea Delays Growth and Accumulation of Key Nutrients in Aerobic Rice but Does Not Affect Grain Mineral Concentrations

Directory of Open Access Journals (Sweden)

Terry J. Rose

2016-01-01

Full Text Available Enhanced efficiency nitrogen (N fertilizers (EEFs may improve crop recovery of fertilizer-N, but there is evidence that some EEFs cause a lag in crop growth compared to growth with standard urea. Biomass and mineral nutrient accumulation was investigated in rice fertilized with urea, urea-3,4-dimethylpyrazole phosphate (DMPP and polymer-coated urea (PCU to determine whether any delays in biomass production alter the accumulation patterns, and subsequent grain concentrations, of key mineral nutrients. Plant growth and mineral accumulation and partitioning to grains did not differ significantly between plants fertilized with urea or urea-DMPP. In contrast, biomass accumulation and the accumulation of phosphorus, potassium, calcium, magnesium, copper, zinc and manganese were delayed during the early growth phase of plants fertilized with PCU. However, plants in the PCU treatment ultimately compensated for this by increasing growth and nutrient uptake during the latter vegetative stages so that no differences in biomass or nutrient accumulation generally existed among N fertilizer treatments at anthesis. Delayed biomass accumulation in rice fertilized with PCU does not appear to reduce the total accumulation of mineral nutrients, nor to have any impact on grain mineral nutrition when biomass and grain yields are equal to those of rice grown with urea or urea-DMPP.

Effect of second phase particles topology on the onset temperature of abnormal grain growth in Fe - 3%Si steels

Directory of Open Access Journals (Sweden)

Stoyka, V.

2008-01-01

Full Text Available The relations between regimes of dynamic annealing, state of secondary particles system and the onset temperature of abnormal grain growth are investigated. Two distinguish types of Fe-3%Si grain-oriented steels, after one and two stage cold rolling, were studied. The second phase particles remain unaffected in first type of steel during the heat treatment. Vice versa, the increased density of second phases was observed after annealing in the second type of the investigated materials. It is shown that start/onset of abnormal grain growth strongly depends on both volume fraction of second phase particles and annealing temperature. Texture and magnetic properties of the investigated samples are investigated within the current study.

Variations in grain lipophilic phytochemicals, proteins and resistance to Fusarium spp. growth during grain storage as affected by biological plant protection with Aureobasidium pullulans (de Bary).

Science.gov (United States)

Wachowska, Urszula; Tańska, Małgorzata; Konopka, Iwona

2016-06-16

Modern agriculture relies on an integrated approach, where chemical treatment is reduced to a minimum and replaced by biological control that involves the use of active microorganisms. The effect of the antagonistic yeast-like fungus Aureobasidium pullulans on proteins and bioactive compounds (alkylresorcinols, sterols, tocols and carotenoids) in winter wheat grain and on the colonization of wheat kernels by fungal microbiota, mainly Fusarium spp. pathogens, was investigated. Biological treatment contributed to a slight increase contents of tocols, alkylresorcinols and sterols in grain. At the same time, the variation of wheat grain proteins was low and not significant. Application of A. pullulans enhanced the natural yeast colonization after six months of grain storage and inhibited growth of F. culmorum pathogens penetrating wheat kernel. This study demonstrated that an integrated approach of wheat grain protection with the use of the yeast-like fungus A. pullulans reduced kernel colonization by Fusarium spp. pathogens and increased the content of nutritionally beneficial phytochemicals in wheat grain without a loss of gluten proteins responsible for baking value. Copyright © 2016. Published by Elsevier B.V.

Densification and grain growth during sintering of porous Ce0.9Gd0.1O1.95tape cast layers: A comprehensive study on heuristic methods

DEFF Research Database (Denmark)

Ni, De Wei; Schmidt, Cristine Grings; Teocoli, Francesca

2013-01-01

The sintering behavior of porous Ce0.9Gd0.1O1.95(CGO10) tape cast layers was systematically investigated to establish fundamental kinetic parameters associated to densification and grain growth. Densification and grain growth were characterized by a set of different methods to determine the domin...... and grain boundary mobility in the porous body was estimated around 10−18–10−16m3N−1s−1 at the investigated temperature range.© 2013 Elsevier Ltd. All rights reserved.......The sintering behavior of porous Ce0.9Gd0.1O1.95(CGO10) tape cast layers was systematically investigated to establish fundamental kinetic parameters associated to densification and grain growth. Densification and grain growth were characterized by a set of different methods to determine...... the dominant sintering mechanisms and kinetics, both in isothermal and at constant heating rate (iso-rate) conditions. Densification of porous CGO10 tape is thermally activated with typical activation energy which was estimated around 440–470 kJ mol−1. Grain growth showed similar thermal activation energy...

Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

International Nuclear Information System (INIS)

Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H.Y.; Fu, B.Q.; Li, M.; Liu, W.

2013-01-01

Highlights: ► Recrystallization temperature of a rolled W was ∼2480 °C under applied HHF loads. ► Fine grains were obtained under HHF loads with appropriate short pulse length. ► With increasing pulse length, the recrystallized grains significantly grew larger. ► A linear relationship between ln d and 1/T max was found. ► Activation energy for grain growth in T evolution up to T max in 1.5 s was obtained. -- Abstract: Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m 2 were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/T max ) was found and accordingly the activation energy for grain growth in temperature evolution up to T max in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads

Study of rapid grain boundary migration in a nanocrystalline Ni thin film

International Nuclear Information System (INIS)

Kacher, Josh; Robertson, I.M.; Nowell, Matt; Knapp, J.; Hattar, Khalid

2011-01-01

Research highlights: → Abnormal growth is distributed randomly in the foil and initiates at different times. → Growth occurs from seemingly uncorrelated regions of the grain boundary. → Growth twins are created during all stages of abnormal grain growth. → Grain growth patterns are qualitatively similar to a vacancy diffusion model. → Grain boundaries and orientations evolve during growth to minimize system energy. - Abstract: Grain boundary migration associated with abnormal grain growth in pulsed-laser deposited Ni was studied in real time by annealing electron transparent films in situ in the transmission electron microscope. The resulting texture evolution and grain boundary types produced were evaluated by ex situ electron backscatter diffraction of interrupted anneals. The combination of these two techniques allowed for the investigation of grain growth rates, grain morphologies, and the evolution of the orientation and grain boundary distributions. Grain boundaries were found to progress in a sporadic, start/stop fashion with no evidence of a characteristic grain growth rate. The orientations of the abnormally growing grains were found to be predominately //ND throughout the annealing process. A high fraction of twin boundaries developed during the annealing process. The intermittent growth from different locations of the grain boundary is discussed in terms of a vacancy diffusion model for grain growth.

Effects of Sb-doping on the grain growth of Cu(In, Ga)Se2 thin films fabricated by means of single-target sputtering

International Nuclear Information System (INIS)

Zhang, Shu; Wu, Lu; Yue, Ruoyu; Yan, Zongkai; Zhan, Haoran; Xiang, Yong

2013-01-01

To investigate the effects of Sb doping on the kinetics of grain growth in Cu(In,Ga)Se 2 (CIGS) thin films during annealing, CIGS thin films were sputtered onto Mo coated substrates from a single CIGS alloy target, followed by chemical bath deposition of Sb 2 S 3 thin layers on top of CIGS layers and subsequent annealing at different temperatures for 30 min in Se vapors. X-ray diffraction results showed that CIGS thin films were obtained directly using the single-target sputtering method. After annealing, the In/Ga ratio in Sb-doped CIGS thin films remained stable compared to undoped film, possibly because Sb can promote the incorporation of Ga into CIGS. The grain growth in CIGS thin films was enhanced after Sb doping, exhibiting significantly larger grains after annealing at 400 °C or 450 °C compared to films without Sb. In particular, the effect was strikingly significant in grain growth across the film thickness, resulting in columnar grain structure in Sb-doped films. This grain growth improvement may be led by the diffusion of Sb from the front surface to the CIGS-Mo back interface, which promoted the mass transport process in CIGS thin films. - Highlights: ► Cu(In,Ga)Se 2 (CIGS) thin films made by sputtering from a single CIGS target. ► Chemical bath deposition used to introduce antimony into CIGS absorber layers. ► In/Ga ratio decreases in Sb-doped annealed films, comparatively to undoped films. ► Sb-doped CIGS films are superior to undoped films in terms of grain-growth kinetics

Drought priming at vegetative growth stages improves tolerance to drought and heat stresses occurring during grain filling in spring wheat

DEFF Research Database (Denmark)

Wang, Xiao; Vignjevic, Marija; Liu, Fulai

2015-01-01

Plants of spring wheat (Triticum aestivum L. cv. Vinjett) were exposed to moderate water deficit at the vegetative growth stages six-leaf and/or stem elongation to investigate drought priming effects on tolerance to drought and heat stress events occurring during the grain filling stage. Compared......Plants of spring wheat (Triticum aestivum L. cv. Vinjett) were exposed to moderate water deficit at the vegetative growth stages six-leaf and/or stem elongation to investigate drought priming effects on tolerance to drought and heat stress events occurring during the grain filling stage...... of abscisic acid in primed plants under drought stress could contribute to higher grain yield compared to the non-primed plants. Taken together, the results indicate that drought priming during vegetative stages improved tolerance to both drought and heat stress events occurring during grain filling in wheat....

The growth mechanism of grain boundary carbide in Alloy 690

International Nuclear Information System (INIS)

Li, Hui; Xia, Shuang; Zhou, Bangxin; Peng, Jianchao

2013-01-01

The growth mechanism of grain boundary M 23 C 6 carbides in nickel base Alloy 690 after aging at 715 °C was investigated by high resolution transmission electron microscopy. The grain boundary carbides have coherent orientation relationship with only one side of the matrix. The incoherent phase interface between M 23 C 6 and matrix was curved, and did not lie on any specific crystal plane. The M 23 C 6 carbide transforms from the matrix phase directly at the incoherent interface. The flat coherent phase interface generally lies on low index crystal planes, such as (011) and (111) planes. The M 23 C 6 carbide transforms from a transition phase found at curved coherent phase interface. The transition phase has a complex hexagonal crystal structure, and has coherent orientation relationship with matrix and M 23 C 6 : (111) matrix //(0001) transition //(111) carbide , ¯ > matrix // ¯ 10> transition // ¯ > carbide . The crystal lattice constants of transition phase are c transition =√(3)×a matrix and a transition =√(6)/2×a matrix . Based on the experimental results, the growth mechanism of M 23 C 6 and the formation mechanism of transition phase are discussed. - Highlights: • A transition phase was observed at the coherent interfaces of M 23 C 6 and matrix. • The transition phase has hexagonal structure, and is coherent with matrix and M 23 C 6 . • The M 23 C 6 transforms from the matrix directly at the incoherent phase interface

Front tracking based modeling of the solid grain growth on the adaptive control volume grid

Science.gov (United States)

Seredyński, Mirosław; Łapka, Piotr

2017-07-01

The paper presents the micro-scale model of unconstrained solidification of the grain immersed in under-cooled liquid, based on the front tracking approach. For this length scale, the interface tracked through the domain is meant as the solid-liquid boundary. To prevent generation of huge meshes the energy transport equation is discretized on the adaptive control volume (c.v.) mesh. The coupling of dynamically changing mesh and moving front position is addressed. Preliminary results of simulation of a test case, the growth of single grain, are presented and discussed.

Nanocrystalline growth and grain-size effects in Au-Cu electrodeposits

International Nuclear Information System (INIS)

Jankowski, Alan F.; Saw, Cheng K.; Harper, Jennifer F.; Vallier, Bobby F.; Ferreira, James L.; Hayes, Jeffrey P.

2006-01-01

The processing-structure-property relationship is investigated for electrodeposited foils of the gold-copper alloy system. A model is presented that relates the deposition process parameters to the nanocrystalline grain size. An activation energy of 1.52 eV atom -1 for growth is determined for a long-pulse (> 10 msec) mode, and is 0.16 eV atom -1 for short pulses ( 6 nm) is observed for Au-Cu samples with 1-12 wt.% Cu as tested in cross-section. The hardness increases three-fold from a rule-of-mixtures value < 1 GPa to a maximum of 2.9 GPa

Influence of water activity and temperature on growth and fumonisin production by Fusarium proliferatum strains on irradiated wheat grains.

Science.gov (United States)

Cendoya, Eugenia; Monge, María Del Pilar; Chiacchiera, Stella Maris; Farnochi, María Cecilia; Ramirez, María Laura

2018-02-02

Wheat is the most important cereal consumed by the Argentine population. In previous studies performed in durum and common wheat grains in this country it has been observed fumonisin contamination as well as high incidence of Fusarium proliferatum. Fumonisins are toxic fungal metabolites, and consumption of fumonisin-contaminated maize has been epidemiologically associated with oesophageal cancer and neural tube defects in some human populations. Using irradiated wheat-grains, the effects of abiotic factors, temperature (15, 25, and 30°C) and water activity (a W ; 0.995, 0.98, 0.96, 0.94, 0.92, and 0.88), on mycelial growth and fumonisin biosynthesis were compared for three F. proliferatum strains isolated from wheat grains in Argentina. Although all isolates showed similar profiles of growth, the fumonisin production profiles were slightly different. Maximum growth rates were obtained at the highest a W (0.995) and 25°C, with growth decreasing as the a W of the medium was reduced. Maximum amounts of total fumonisins (FB 1 , FB 2 and FB 3 ) were produced at 0.995 a W and 15°C for 2 strains, and at 25°C and 0.995 a W for the third one. Fumonisins concentrations varied considerably depending on the a W and temperature interactions assayed. Studied strains showed different fumonisin production profiles. Two-dimensional profiles of a W by temperature interactions were developed from these data to identify areas where conditions indicate a significant risk of fumonisins accumulation on wheat. As a result, temperature and a W conditions that resulted in fumonisins production are those found during wheat grain development (especially milk and dough stages) in the field. This is the first study made using irradiated wheat grains and provides useful baseline data on conditions representing a low or a high risk for fumonisins contamination of wheat grains which is of concern because this cereal is destined mainly for human consumption. Copyright © 2017 Elsevier B.V. All

The W alloying effect on thermal stability and hardening of nanostructured Cu–W alloyed thin films

Science.gov (United States)

Zhao, J. T.; Zhang, J. Y.; Hou, Z. Q.; Wu, K.; Feng, X. B.; Liu, G.; Sun, J.

2018-05-01

In order to achieve desired mechanical properties of alloys by manipulating grain boundaries (GBs) via solute decoration, it is of great significance to understand the underlying mechanisms of microstructural evolution and plastic deformation. In this work, nanocrystalline (NC) Cu–W alloyed films with W concentrations spanning from 0 to 40 at% were prepared by using magnetron sputtering. Thermal stability (within the temperature range of 200 °C–600 °C) and hardness of the films were investigated by using the x-ray diffraction, transmission electron microscope (TEM) and nanoindentation, respectively. The NC pure Cu film exhibited substantial grain growth upon all annealing temperatures. The Cu–W alloyed films, however, displayed distinct microstructural evolution that depended not only on the W concentration but also on the annealing temperature. At a low temperature of 200 °C, all the Cu–W alloyed films were highly stable, with unconspicuous change in grain sizes. At high temperatures of 400 °C and 600 °C, the microstructural evolution was greatly controlled by the W concentrations. The Cu–W films with low W concentration manifested abnormal grain growth (AGG), while the ones with high W concentrations showed phase separation. TEM observations unveiled that the AGG in the Cu–W alloyed thin films was rationalized by GB migration. Nanoindentation results showed that, although the hardness of both the as-deposited and annealed Cu–W alloyed thin films monotonically increased with W concentrations, a transition from annealing hardening to annealing softening was interestingly observed at the critical W addition of ∼25 at%. It was further revealed that an enhanced GB segregation associated with detwinning was responsible for the annealing hardening, while a reduced solid solution hardening for the annealing softening.

The W alloying effect on thermal stability and hardening of nanostructured Cu-W alloyed thin films.

Science.gov (United States)

Zhao, J T; Zhang, J Y; Hou, Z Q; Wu, K; Feng, X B; Liu, G; Sun, J

2018-05-11

In order to achieve desired mechanical properties of alloys by manipulating grain boundaries (GBs) via solute decoration, it is of great significance to understand the underlying mechanisms of microstructural evolution and plastic deformation. In this work, nanocrystalline (NC) Cu-W alloyed films with W concentrations spanning from 0 to 40 at% were prepared by using magnetron sputtering. Thermal stability (within the temperature range of 200 °C-600 °C) and hardness of the films were investigated by using the x-ray diffraction, transmission electron microscope (TEM) and nanoindentation, respectively. The NC pure Cu film exhibited substantial grain growth upon all annealing temperatures. The Cu-W alloyed films, however, displayed distinct microstructural evolution that depended not only on the W concentration but also on the annealing temperature. At a low temperature of 200 °C, all the Cu-W alloyed films were highly stable, with unconspicuous change in grain sizes. At high temperatures of 400 °C and 600 °C, the microstructural evolution was greatly controlled by the W concentrations. The Cu-W films with low W concentration manifested abnormal grain growth (AGG), while the ones with high W concentrations showed phase separation. TEM observations unveiled that the AGG in the Cu-W alloyed thin films was rationalized by GB migration. Nanoindentation results showed that, although the hardness of both the as-deposited and annealed Cu-W alloyed thin films monotonically increased with W concentrations, a transition from annealing hardening to annealing softening was interestingly observed at the critical W addition of ∼25 at%. It was further revealed that an enhanced GB segregation associated with detwinning was responsible for the annealing hardening, while a reduced solid solution hardening for the annealing softening.

The use of thermally stimulated depolarization currents to study grain growth in ceramic thorium dioxide

International Nuclear Information System (INIS)

Muccillo, R.; Campos, L.L.

1979-01-01

Depolarization Current Spectra resulting from the destruction of the thermoelectret state in polycrystalline ThO 2 samples have been detected in the temperature range 100K-350K. The induced polarization is found to be due to migration of charge carriers over microscopic distances in the bulk of the specimens with trapping at grain boundaries. Moreover the density of charge carriers released from trapping sites, upon heating the cooled previously dc biased specimen decreases for increasing sintering temperature, suggesting the use of the technique to the study of grain growth in the bulk of ceramic oxides. (Author) [pt

Fission gas release and grain growth in THO2-UO2 fuel irradiated at high temperature

International Nuclear Information System (INIS)

Goldberg, I.; Waldman, L.A.; Giovengo, J.F.; Campbell, W.R.

1979-01-01

Data are presented on fission gas release and grain growth in ThO 2 -UO 2 fuels irradiated as part of the LWBR fuel element development program. These data for rods that experienced peak linear power outputs ranging from 15 to 22 KW/ft supplement fission gas release data previously reported for 51 rods containing ThO 2 and ThO 2 -UO 2 fuel irradiated at peak linear powers predominantly below 14 KW/ft. Fission gas release was relatively high (up to 15.0 percent) for the rods operated at high power in contrast to the relatively low fission gas release (0.1 to 5.2 percent) measured for the rods operated at lower power. Metallographic examination revealed extensive equiaxed grain growth in the fuel at the high power axial locations of the three rods

Grain Formation Processes in Oxygen-Rich Circumstellar Outflows: Testing the Metastable Eutectic Condensation Hypothesis and Measuring Atom-Grain & Grain-Grain Sticking Coefficients (A Sub-orbital Investigation)

Science.gov (United States)

Nuth, Joseph

An experimentally-based model of grain formation in oxygen-rich circumstellar outflows that includes vapor-solid nucleation, grain growth, thermal annealing and grain aggregation in sufficient detail to predict the spectral energy distribution (SED) of the shells for comparison with observations of a wide range of stellar sources still lacks critical data. In order to gather this data we propose to conduct a series of laboratory experiments using our proven experimental system and microgravity condensation, growth and grain aggregation experiments on sounding rockets with a flight-proven payload provided by Dr. Yuki Kimura of Hokkaido University. We have proposed that solids from a hydrogen-rich, supersaturated, Fe-Mg-SiO vapor condense at metastable eutectic points in this ternary phase diagram. Because the FeOMgO system is totally miscible (has no eutectic or metastable eutectic compositions), this predicts that condensates will be pure Mg-silicate or Fe-silicate grains and that no primary condensate will be a mixed Fe-Mg-silicate. We have shown that this observation leads to a logical explanation as to why pure magnesium olivine and enstatite minerals are detected in circumstellar winds rather than the mixed Mg-Fe-silicate grains that might otherwise be expected (Rietmeijer, Nuth & Karner, 1999). This simplifying hypothesis has been built into our models of circumstellar condensation and growth. However, these experimental results require confirmation and testing since they should apply to other, quite similar condensable systems. We propose to test this hypothesis by condensing solids from the Fe-Mg-AlO ternary vapor system. Since FeO-MgO miscibility also applies to this system, the primary condensates from such a vapor should consist of pure amorphous Fe-aluminates and Mg-aluminates. No mixed Fe-Mg-spinels should be detected as primary condensates if this hypothesis is correct, just as none were detected for the FeO-MgO-SiO system. Confirmation of this

Abrus agglutinin promotes irreparable DNA damage by triggering ROS generation followed by ATM-p73 mediated apoptosis in oral squamous cell carcinoma.

Science.gov (United States)

Sinha, Niharika; Panda, Prashanta K; Naik, Prajna P; Das, Durgesh N; Mukhopadhyay, Subhadip; Maiti, Tapas K; Shanmugam, Muthu K; Chinnathambi, Arunachalam; Zayed, M E; Alharbi, Sulaiman A; Sethi, Gautam; Agarwal, Rajesh; Bhutia, Sujit K

2017-11-01

Oral cancer, a type of head and neck cancer, is ranked as one of the top most malignancies in India. Herein, we evaluated the anticancer efficacy of Abrus agglutinin (AGG), a plant lectin, in oral squamous cell carcinoma. AGG selectively inhibited cell growth, and caused cell cycle arrest and mitochondrial apoptosis through a reactive oxygen species (ROS)-mediated ATM-p73 dependent pathway in FaDu cells. AGG-induced ROS accumulation was identified as the major mechanism regulating apoptosis, DNA damage and DNA-damage response, which were significantly reversed by ROS scavenger N-acetylcysteine (NAC). Moreover, AGG was found to interact with mitochondrial manganese-dependent superoxide dismutase that might inhibit its activity and increase ROS in FaDu cells. In oral cancer p53 is mutated, thus we focused on p73; AGG resulted in p73 upregulation and knock down of p73 caused a decrease in AGG-induced apoptosis. Interestingly, AGG-dependent p73 expression was found to be regulated by ROS, which was reversed by NAC treatment. A reduction in the level of p73 in AGG-treated shATM cells was found to be associated with a decreased apoptosis. Moreover, administration of AGG (50 μg/kg body weight) significantly inhibited the growth of FaDu xenografts in athymic nude mice. In immunohistochemical analysis, the xenografts from AGG-treated mice displayed a decrease in PCNA expression and an increase in caspase-3 activation as compared to the controls. In conclusion, we established a connection among ROS, ATM and p73 in AGG-induced apoptosis, which might be useful in enhancing the therapeutic targeting of p53 deficient oral squamous cell carcinoma. © 2017 Wiley Periodicals, Inc.

Identification, quantification, spatiotemporal distribution and genetic variation of major latex secondary metabolites in the common dandelion (Taraxacum officinale agg.).

Science.gov (United States)

Huber, Meret; Triebwasser-Freese, Daniella; Reichelt, Michael; Heiling, Sven; Paetz, Christian; Chandran, Jima N; Bartram, Stefan; Schneider, Bernd; Gershenzon, Jonathan; Erb, Matthias

2015-07-01

The secondary metabolites in the roots, leaves and flowers of the common dandelion (Taraxacum officinale agg.) have been studied in detail. However, little is known about the specific constituents of the plant's highly specialized laticifer cells. Using a combination of liquid and gas chromatography, mass spectrometry and nuclear magnetic resonance spectrometry, we identified and quantified the major secondary metabolites in the latex of different organs across different growth stages in three genotypes, and tested the activity of the metabolites against the generalist root herbivore Diabrotica balteata. We found that common dandelion latex is dominated by three classes of secondary metabolites: phenolic inositol esters (PIEs), triterpene acetates (TritAc) and the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G). Purification and absolute quantification revealed concentrations in the upper mgg(-1) range for all compound classes with up to 6% PIEs, 5% TritAc and 7% TA-G per gram latex fresh weight. Contrary to typical secondary metabolite patterns, concentrations of all three classes increased with plant age. The highest concentrations were measured in the main root. PIE profiles differed both quantitatively and qualitatively between plant genotypes, whereas TritAc and TA-G differed only quantitatively. Metabolite concentrations were positively correlated within and between the different compound classes, indicating tight biosynthetic co-regulation. Latex metabolite extracts strongly repelled D. balteata larvae, suggesting that the latex constituents are biologically active. Copyright © 2015 Elsevier Ltd. All rights reserved.

Grain growth: The key to understand solid-state dewetting of silver thin films

International Nuclear Information System (INIS)

Jacquet, P.; Podor, R.; Ravaux, J.; Teisseire, J.; Gozhyk, I.; Jupille, J.; Lazzari, R.

2016-01-01

The dynamics of solid-state dewetting of polycrystalline silver thin films in oxygen atmosphere was investigated with in situ and real-time environmental Scanning Electron Microscopy at high temperature combined with Atomic Force Microscopy. Three steps were identified during dewetting: induction, hole propagation without specific rim and sintering. Moreover, it was observed that a very selective grain growth, promoted by surface diffusion, plays a key role all along the process.

Grain centre mapping - 3DXRD measurements of average grain characteristics

DEFF Research Database (Denmark)

Oddershede, Jette; Schmidt, Søren; Lyckegaard, Allan

2014-01-01

characteristics of each grain (such as their centre-of-mass positions, volumes, phases, orientations and/or elastic strain tensor components), while the exact locations of the grain boundaries are unknown. In the present chapter a detailed description of the setup and software for both grain centre mapping...... and the closely related boxscan method is given. Both validation experiments and applications for in situ studies of microstructural changes during plastic deformation and crack growth are given. Finally an outlook with special emphasis on coupling the measured results with modelling is given....

Grain growth effects on magnetic properties of Ni0.6Zn0.4Fe2O4 material prepared using mechanically alloyed nanoparticles

Science.gov (United States)

Syazwan, M. M.; Hapishah, A. N.; Azis, R. S.; Abbas, Z.; Hamidon, M. N.

2018-06-01

The effect of grain growth via sintering temperature on some magnetic properties is reported in this research. Ni0.6Zn0.4Fe2O4 nanoparticles were mechanically alloyed for 6 h and the sintering process starting from 600 to 1200 °C with 25 °C increment with only one sample subjected to all sintering scheme. The resulting change in the material was observed after each sintering. Single phase has been formed at 600 °C and above and the intensity peaks increased with sintering temperature as well as crystallinity increment. The morphological studies showed grain size increment as the sintering temperature increased. Moreover, the density increased while the porosity decreased with increasing sintering temperature. The saturation induction, Bs increased with the increased of grain size. On the other hand, the coercivity-vs-grain size plot reveals the critical single-domain-to-multidomain grain size to be about ∼400 nm. The initial permeability, μi value was increased with grain size enhancement. The microstructural grain growth, as exposed for the first time by this research, is shown as a process of multiple activation energy barriers.

Analytical expression for the evolution of interfacial area density between transformed grains during nucleation and growth transformations

DEFF Research Database (Denmark)

Rios, P.R.; Godiksen, R.B.; Schmidt, Søren

2006-01-01

This paper shows that interfacial area density between transformed grains during nucleation and growth transformations and the contiguity are useful descriptors of microstructural evolution. These descriptors are evaluated analytically and compared with results from computer simulation. Usage...

DUST PROPERTIES AND DISK STRUCTURE OF EVOLVED PROTOPLANETARY DISKS IN Cep OB2: GRAIN GROWTH, SETTLING, GAS AND DUST MASS, AND INSIDE-OUT EVOLUTION

International Nuclear Information System (INIS)

Sicilia-Aguilar, Aurora; Henning, Thomas; Dullemond, Cornelis P.; Bouwman, Jeroen; Sturm, Bernhard; Patel, Nimesh; Juhász, Attila

2011-01-01

We present Spitzer/Infrared Spectrograph spectra of 31 T Tauri stars (TTS) and IRAM/1.3 mm observations for 34 low- and intermediate-mass stars in the Cep OB2 region. Including our previously published data, we analyze 56 TTS and 3 intermediate-mass stars with silicate features in Tr 37 (∼4 Myr) and NGC 7160 (∼12 Myr). The silicate emission features are well reproduced with a mixture of amorphous (with olivine, forsterite, and silica stoichiometry) and crystalline grains (forsterite, enstatite). We explore grain size and disk structure using radiative transfer disk models, finding that most objects have suffered substantial evolution (grain growth, settling). About half of the disks show inside-out evolution, with either dust-cleared inner holes or a radially dependent dust distribution, typically with larger grains and more settling in the innermost disk. The typical strong silicate features nevertheless require the presence of small dust grains, and could be explained by differential settling according to grain size, anomalous dust distributions, and/or optically thin dust populations within disk gaps. M-type stars tend to have weaker silicate emission and steeper spectral energy distributions than K-type objects. The inferred low dust masses are in a strong contrast with the relatively high gas accretion rates, suggesting global grain growth and/or an anomalous gas-to-dust ratio. Transition disks in the Cep OB2 region display strongly processed grains, suggesting that they are dominated by dust evolution and settling. Finally, the presence of rare but remarkable disks with strong accretion at old ages reveals that some very massive disks may still survive to grain growth, gravitational instabilities, and planet formation.

Microstructural characterization and grain growth kinetics of atomized Fe-6%Si alloy

Energy Technology Data Exchange (ETDEWEB)

Florio Filho, A.; Bolfarini, C.; Kiminami, C.S. [Dept. de Engenharia de Materiais, Univ. Federal de Sao Carlos, Sao Carlos SP (Brazil)

2001-07-01

The microstructural characterization of the overspray powders is considered an important step to evaluate the as-cast microstructure of preforms fabricated by spray forming process. The particles generated during the high pressure gas atomization fly toward a substrate located at the middle height into the atomization chamber and consolidate to a dense deposit. The solidification process begins already during the flight of the droplets and high cooling rate can be achieved by the droplets of the molten metal during the atomization step. Consequently, the microstructure of the preform has some typical features presented by rapidly solidified metals as low level of porosity and segregation and it is strongly influenced by the thermal history of the droplets during flight. In the present work the microstructure of the particles of the Fe-6%Si alloy was analysed by light microscopy and scanning electron microscopy (SEM). The experimental determination of the kinetic exponent n for grain boundary migration in both powder and preform was determined by isothermal treatment under argon atmosphere. It has been stated that the larger the particle size the greater the grain size in Fe-6%Si alloy. It was observed also that the interface morphology is strongly related to the particle size. Furthermore, the grain growth kinetic in the preform seems to not obey the migration mechanism where the self diffusion of elemental Fe drive the boundary displacement. (orig.)

Electric-Loading Enhanced Kinetics in Oxide Ceramics: Pore Migration, Sintering and Grain Growth: Final Report

Energy Technology Data Exchange (ETDEWEB)

Chen, I-Wei [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science & Engineering

2018-02-02

Solid oxide fuel cells and solid oxide electrolysis cells rely on solid electrolytes in which a large ionic current dominates. This project was initiated to investigate microstructural changes in such devices under electrochemical forces, because nominally insignificant processes may couple to the large ionic current to yield non-equilibrium phenomena that alter the microstructure. Our studies had focused on yttria-stabilized cubic zirconia (YSZ) widely used in these devices. The experiments have revealed enhanced grain growth at higher temperatures, pore and gas bubble migration at all temperatures, and the latter also lead to enhanced sintering of highly porous ceramics into fully dense ceramics at unprecedentedly low temperatures. These results have shed light on kinetic processes that fall completely outside the realm of classical ceramic processing. Other fast-oxygen oxide ceramics closely related to, and often used in conjunction with zirconia ceramics, have also be investigated, as are closely related scientific problems in zirconia ceramics. These include crystal structures, defects, diffusion kinetics, oxygen potentials, low temperature sintering, flash sintering, and coarsening theory, and all have resulted in greater clarity in scientific understanding. The knowledge is leveraged to provide new insight to electrode kinetics and near-electrode mixed conductivity and to new materials. In the following areas, our research has resulted in completely new knowledge that defines the state-of-the-art of the field. (a) Electrical current driven non-equilibrium phenomena, (b) Enhanced grain growth under electrochemically reducing conditions, (c) Development of oxygen potential polarization in electrically loaded electrolyte, (d) Low temperature sintering and grain growth, and (e) Structure, defects and cation kinetics of fluorite-structured oxides. Our research has also contributed to synthesis of new energy-relevant electrochemical materials and new understanding

SPECTROSCOPIC INFRARED EXTINCTION MAPPING AS A PROBE OF GRAIN GROWTH IN IRDCs

Energy Technology Data Exchange (ETDEWEB)

Lim, Wanggi [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Carey, Sean J. [Infrared Processing Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Tan, Jonathan C. [Departments of Astronomy and Physics, University of Florida, Gainesville, FL 32611 (United States)

2015-11-20

We present spectroscopic tests of MIR to FIR extinction laws in IRDC G028.36+00.07, a potential site of massive star and star cluster formation. Lim and Tan developed methods of FIR extinction mapping of this source using Spitzer-MIPS 24 μm and Herschel-PACS 70 μm images, and by comparing to MIR Spitzer-IRAC 3–8 μm extinction maps, found tentative evidence for grain growth in the highest mass surface density regions. Here we present results of spectroscopic infrared extinction mapping using Spitzer-IRS (14–38 μm) data of the same Infrared dark cloud (IRDC). These methods allow us to first measure the SED of the diffuse Galactic interstellar medium that is in the foreground of the IRDC. We then carry out our primary investigation of measuring the MIR to FIR opacity law and searching for potential variations as a function of mass surface density within the IRDC. We find relatively flat, featureless MIR–FIR opacity laws that lack the ∼12 and ∼35 μm features associated with the thick water ice mantle models of Ossenkopf and Henning. Their thin ice mantle models and the coagulating aggregate dust models of Ormel et al. are a generally better match to the observed opacity laws. We also find evidence for generally flatter MIR to FIR extinction laws as mass surface density increases, strengthening the evidence for grain and ice mantle growth in higher density regions.

SPECTROSCOPIC INFRARED EXTINCTION MAPPING AS A PROBE OF GRAIN GROWTH IN IRDCs

International Nuclear Information System (INIS)

Lim, Wanggi; Carey, Sean J.; Tan, Jonathan C.

2015-01-01

We present spectroscopic tests of MIR to FIR extinction laws in IRDC G028.36+00.07, a potential site of massive star and star cluster formation. Lim and Tan developed methods of FIR extinction mapping of this source using Spitzer-MIPS 24 μm and Herschel-PACS 70 μm images, and by comparing to MIR Spitzer-IRAC 3–8 μm extinction maps, found tentative evidence for grain growth in the highest mass surface density regions. Here we present results of spectroscopic infrared extinction mapping using Spitzer-IRS (14–38 μm) data of the same Infrared dark cloud (IRDC). These methods allow us to first measure the SED of the diffuse Galactic interstellar medium that is in the foreground of the IRDC. We then carry out our primary investigation of measuring the MIR to FIR opacity law and searching for potential variations as a function of mass surface density within the IRDC. We find relatively flat, featureless MIR–FIR opacity laws that lack the ∼12 and ∼35 μm features associated with the thick water ice mantle models of Ossenkopf and Henning. Their thin ice mantle models and the coagulating aggregate dust models of Ormel et al. are a generally better match to the observed opacity laws. We also find evidence for generally flatter MIR to FIR extinction laws as mass surface density increases, strengthening the evidence for grain and ice mantle growth in higher density regions

Branching-induced grain boundary evolution during directional solidification of columnar dendritic grains

International Nuclear Information System (INIS)

Guo, Chunwen; Li, Junjie; Yu, Honglei; Wang, Zhijun; Lin, Xin; Wang, Jincheng

2017-01-01

We present an investigation of secondary and tertiary branching behavior in diverging grain boundaries (GBs) between two columnar dendritic grains with different crystallographic orientations, both by two-dimensional phase-field simulations and thin-sample experiments. The stochasticity of the GB trajectories and the statistically averaged GB orientations were analyzed in detail. The side-branching dynamics and subsequent branch competition behaviors found in the simulations agreed well with the experimental results. When the orientations of two grains are given, the experimental results indicated that the average GB orientation was independent of the pulling velocity in the dendritic growth regime. The simulation and experimental results, as well as the results reported in the literature exhibit a uniform relation between the percentage of the whole gap region occupied by the favorably oriented grain and the difference in the absolute values of the secondary arm growth directions of the two competitive grains. By describing such a uniform relation with a simple fitting equation, we proposed a simple analytical model for the GB orientation at diverging GBs, which gives a more accurate description of GB orientation selection than the existing models.

Effects of Grain Boundaries and Dislocation Cell Walls on Void Nucleation and Growth in Aluminium during Fast Neutron Irradiation

DEFF Research Database (Denmark)

Horsewell, Andy; Rahman, F. A.; Singh, Bachu Narain

1983-01-01

and growth occurs in a zone extending up to 10 mu m from grain boundaries in annealed material. In polygonized material, the presence of dislocation cell walls leads to cell size dependent void formation and growth; the swelling rate in the large cells is substantially higher than in the annealed material....

Rate and Timing Effects of Growth Regulating Herbicides Applications on Grain Sorghum (Sorghum bicolor Growth and Yield

Directory of Open Access Journals (Sweden)

Thierry E. Besançon

2016-01-01

Full Text Available Dicamba and 2,4-D are among the most common and inexpensive herbicides used to control broadleaf weeds. However, different studies have pointed the risk of crop injury and grain sorghum yield reduction with postemergence applications of 2,4-D. No research data on grain sorghum response to 2,4-D or dicamba exists in the Southeastern United States. Consequently, a study was conducted to investigate crop growth and yield response to 2,4-D (100, 220, and 330 g acid equivalent ha−1 and dicamba (280 g acid equivalent ha−1 applied on 20 to 65 cm tall sorghum. Greater stunting resulted from 2,4-D applied at 330 g acid equivalent ha−1 or below 45 cm tall sorghum whereas lodging prevailed with 2,4-D at 330 g acid equivalent ha−1 and dicamba applied beyond 35 cm tall crop. Regardless of local environmental conditions, 2,4-D applied up to 35 cm tall did not negatively impact grain yield. There was a trend for yields to be somewhat lower when 2,4-D was applied on 45 or 55 cm tall sorghum whereas application on 65 cm tall sorghum systematically decreased yields. More caution should be taken with dicamba since yield reduction has been reported as early as applications made on 35 cm tall sorghum for a potentially dicamba sensitive cultivar.

Silicon treatment to rice (oryza sativa l. cv 'gopumbyeo') plants during different growth periods and its effects on growth and grain yield

International Nuclear Information System (INIS)

Kim, Y.H.; Waqas, M.; Kamran, M.

2012-01-01

Silicon (Si) has been considered a beneficial element for plant growth. We have assessed the effects of Si application on rice (Oryza sativa L.) growth and its grain yield at field level. For this, we performed two experiments. In experiment 1, we applied Si of three different concentrations (liquid Si-10, 25 and 36%) to the seedbed of rice before transplantation into paddy field. The results of this experiment showed that Si application to rice seedbeds did not affected the rice plant height and shoot fresh weight but its application significantly increased the pushing resistance of rice plants from 12.2-16.7% as compared with water applied control plants. The lodging index of Si treated rice plants significantly decreased (13.7% on LS-25) as compared with control. Similarly, Si treated plants had significantly higher yield. Upon Si treatment (LS-36), the grain yield per 10 acre and panicles per plant were 15.1% and 6. 3% higher than the water treated control plants respectively. The best concentration (LS-36%) revealed in the first experiment was foliar applied at 10 days before heading stage, initial tilling stage and panicle initiation stage to the rice leaves and we observed that shoot biomass was not significantly different between control and Si treated plants. However, significantly higher pushing resistance (10.5%-13.8%) and plant height (12.2%-16.7%) were observed while lower lodging index (7.6-7.8%) was recorded for Si treated plants as compared to control plants. Similarly, Si application increased the number of panicles per plant as well as the grain yield per 10 acre as compared to control. In conclusion, the Si application can significantly regulate plant growth and yield if applied at proper time with feasible concentration. (author)

Dynamic recrystallization and grain growth in olivine rocks

NARCIS (Netherlands)

Kellermann Slotemaker, A.

2006-01-01

A mechanism based description of the rheology of olivine is essential for modeling of upper mantle geodynamics. Previously, mantle flow has been investigated using flow laws for grain size insensitive (GSI) dislocation creep and/or grain size sensitive (GSS) diffusion creep of olivine. Generally,

Grain Boundary Engineering of Electrodeposited Thin Films

DEFF Research Database (Denmark)

Alimadadi, Hossein

is not yet well-understood. This, at least partly, owes to the lack of robust characterization methods for analyzing the nature of grain boundaries including the grain boundary plane characteristics, until recently. In the past decade, significant improvements in the 2-dimensional and 3-dimensional analysis...... of the favorable boundaries that break the network of general grain boundaries. Successful dedicated synthesis of a textured nickel film fulfilling the requirements of grain boundary engineered materials, suggests improved boundary specific properties. However, the textured nickel film shows fairly low...... thermal stability and growth twins annihilate by thermal treatment at 600 degree C. In contrast, for oriented grains, growth nano-twins which are enveloped within columnar grains show a high thermal stability even after thermal treatment at 600 degree C. In order to exploit the high thermal...

Effect of Plant Growth Promoting Rhizobacteria (PGPR on Phenological Traits, Grain Yield and Yield Components of Three Maize (Zea mays L. Cultivars

Directory of Open Access Journals (Sweden)

A Soleimani Fard

2013-11-01

Full Text Available To evaluate the effect of bio-fertilize on yield and its components in maize cultivars, an split plot experiment based on randomized complete bock design with three replications in was conducted in Payam-noor University of Ilam, Iran, in 2009-2010. Treatments were cultivar (SC604, SC704 and SC807 assigned to main plots and bio-fertilizer (non- inoculation, inoculation with Azetobacter, Azospirillum and dual inoculation ofAzotobacterand Azospirillum to subplots. The effect of cultivar on days to maturity, plant height, dry matter, ear length, stem diameter, number of grain per ear row, 1000-grain weight, grain yield, biological yield and protein content was significant cultivar. SC 704 had the highest dry matter (259.5 g.m-2, plant height (201.1 cm, number of grain per ear row (42.8 grain, grain yield (10850 kg.m-2, and biological yield (22040 kg.m-2. The effect of plant growth promoting rhizobacteria on all traits expect harvest index was significant. Dual inoculation ofAzotobacterand Azospirillum had the longest days to ear initiation (71.2 days, days to maturity (115.4 day, number of leaves above ear (5.6 ear, dry matter (240.4 g.m-2, ear length (24.3 cm, plant height (212.4 cm, seed number of rows per ear (14.5 row, number of grains per row (44.2 grain, grain yield (10190 kg.m-2, biological yield (21320 kg.m-2 and protein content (10.7%. Interaction effect of cultivar× plant growth promoting rhizobacteria on grain yield was significant. The highest and lowest grain yield was obtained from SC 704 and application of dual inoculation ofAzotobacterand Azospirillum (12320 kg.ha-1 and lowest from SC 604 when inoculation treatments were not used 7570 kg.ha-1 respectively.

Effect of salinity on grain yield and grain quality of wheat (triticum aestivum l.)

International Nuclear Information System (INIS)

Abbas, G.; Saqib, M.; Rafique, Q.; Rahman, A.U.; Akhtar, J.; Haq, M.A.U.

2013-01-01

Salinity is one of the important stresses resulting in the reduction of growth and yield of different crops including wheat. In saline soils the concentration of Na/sup +/ and Cl/sup -/ is higher accompanied with the decreased K/sup +/: Na/sup +/ ratio thus severely affecting the growth and yield of crops. The effect of salinity on the growth and yield of wheat is well documented, whereas there is very little information about salinity tolerance and grain quality of wheat. Present study was conducted to assess the effect of salinity on yield components, ionic relations and grain quality and to understand the relationship among these parameters. A pot experiment was conducted using wheat genotype Pasban-90. There were two treatments i.e. non-saline (0.33 dS m/sup -1/) and saline (15 dS m/sup -1/) with five replications. Salinity resulted in a significant reduction of the grain protein, fat and fiber contents. Similarly yield components were significantly reduced. Maximum reduction was noted in case of number of tillers plant/sup -1/, followed by grain weight plant/sup -1/. High Na/sup +/ and low K/sup +/, P concentration and K/sup +/: Na/sup +/ ratio was observed in the shoot, root and grain. This disturbed ionic composition seems to be apparent cause of yield reduction and deterioration of wheat quality under salinity. (author)

Influence of porosity on densification and grain growth kinetics of Ce_0.9Gd_0.1O_1.95 tape

DEFF Research Database (Denmark)

Ni, De Wei; Esposito, Vincenzo; Foghmoes, Søren Preben Vagn

porous layer allowing gas flow is necessary in catalytic and in gas purification devices. During the sintering with shrinkage, the total solid volume is maintained to be a constant value but the shape and size of each particle change with the formation of grain boundaries. This change in solid particles...... is accompanied by the change of shape, size and fraction of pores in a given volume. Therefore, porosity can be treated as an extra phase during sintering study. In this work, we presented the densification and grain growth behaviour of Ce0.9Gd0.1O1.95 tape cast layers with different percentage of porosity....... The emphasis was put on the effect of porosity on densification and grain growth kinetics. Derived from the sintering constitutive laws, the densification and grain growth kinetics were experimentally characterized and analyzed. Furthermore, the activation energies for viscous flow were determined from master...

Formation of dust grains in the ejecta of SN 1987A

International Nuclear Information System (INIS)

Kozasa, Takashi; Hasegawa, Hiroichi; Nomoto, Kenichi

1989-01-01

Formation of dust grains in the ejecta of SN 1987A is investigated on the basis of a theory of homogeneous nucleation and grain growth. The formation of dust grains in the gas ejected from a heavy element-rich mantle is considered, including the effects of latent heat released during grain growth and of radiation from the photosphere. It is shown that dust grains can condense in the heavy-element-rich mantle, and that the time of formation strongly depends on the temperature structure in the ejecta. Moreover, the formation of dust grains is retarded by the strong SN radiation field and the effect of latent heat deposited during grain growth. 41 refs

CONSTRAINTS ON THE RADIAL VARIATION OF GRAIN GROWTH IN THE AS 209 CIRCUMSTELLAR DISK

International Nuclear Information System (INIS)

Pérez, Laura M.; Carpenter, John M.; Isella, Andrea; Ricci, Luca; Sargent, Anneila I.; Chandler, Claire J.; Andrews, Sean M.; Harris, Robert J.; Calvet, Nuria; Corder, Stuartt A.; Deller, Adam T.; Dullemond, Cornelis P.; Linz, Hendrik; Greaves, Jane S.; Henning, Thomas; Kwon, Woojin; Lazio, Joseph; Mundy, Lee G.; Storm, Shaye; Testi, Leonardo

2012-01-01

We present dust continuum observations of the protoplanetary disk surrounding the pre-main-sequence star AS 209, spanning more than an order of magnitude in wavelength from 0.88 to 9.8 mm. The disk was observed with subarcsecond angular resolution (0.''2-0.''5) to investigate radial variations in its dust properties. At longer wavelengths, the disk emission structure is notably more compact, providing model-independent evidence for changes in the grain properties across the disk. We find that physical models which reproduce the disk emission require a radial dependence of the dust opacity κ ν . Assuming that the observed wavelength-dependent structure can be attributed to radial variations in the dust opacity spectral index (β), we find that β(R) increases from β 1.5 for R ∼> 80 AU, inconsistent with a constant value of β across the disk (at the 10σ level). Furthermore, if radial variations of κ ν are caused by particle growth, we find that the maximum size of the particle-size distribution (a max ) increases from submillimeter-sized grains in the outer disk (R ∼> 70 AU) to millimeter- and centimeter-sized grains in the inner disk regions (R ∼ max (R) with predictions from physical models of dust evolution in protoplanetary disks. For the dust composition and particle-size distribution investigated here, our observational constraints on a max (R) are consistent with models where the maximum grain size is limited by radial drift.

Crystallographic investigation of grain selection during initial solidification

International Nuclear Information System (INIS)

Esaka, H; Shinozuka, K; Kataoka, Y

2016-01-01

Normally, macroscopic solidified structure consists of chill, columnar and equiaxed zones. In a chill zone, many fine grains nucleate on the mold surface and grow their own preferred growth direction. Only a few of them continue to grow because of grain selection. In order to understand the grain selection process, crystallographic investigation has been carried out in the zone of initial solidification in this study. 10 g of Al-6 wt%Si alloy was melted at 850 °C and poured on the thick copper plate. Longitudinal cross section of the solidified shell was observed by a SEM and analyzed by EBSD. The result of EBSD mapping reveals that crystallographic orientation was random in the range of initial solidification. Further, some grains are elongated along their <100> direction. Columnar grains, whose growth directions are almost parallel to the heat flow direction, develop via grain selection. Here, a dendrite whose growth direction is close to the heat flow direction overgrows the other dendrite whose growth direction is far from the heat flow direction. However, sometimes we observed that dendrite, whose zenith angle is large, overgrew the other dendrite. It can be deduced that the time of nucleation on the mold surface is not constant. (paper)

Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

Science.gov (United States)

Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H. Y.; Fu, B. Q.; Li, M.; Liu, W.

2013-02-01

Short pulse heat loads expected for vertical displacement events (VDEs) in ITER were applied in the high heat flux (HHF) test facility GLADIS at IPP-Garching onto samples of rolled W. Pulsed neutral beams with the central heat flux of 23 MW/m2 were applied for 0.5, 1.0 and 1.5 s, respectively. Rapid recrystallization of the adiabatically loaded 3 mm thick samples was observed when the pulse duration was up to 1.0 s. Grains grew markedly following recrystallization with increasing pulse length. The recrystallization temperature and temperature dependence of the recrystallized grain size were also investigated. The results showed that the recrystallization temperature of the W grade was around 2480 °C under the applied heat loading condition, which was nearly 1150 °C higher than the conventional recrystallization temperature, and the grains were much finer. A linear relationship between the logarithm of average grain size (ln d) and the inverse of maximum surface temperature (1/Tmax) was found and accordingly the activation energy for grain growth in temperature evolution up to Tmax in 1.5 s of the short pulse HHF load was deduced to be 4.1 eV. This provided an effective clue to predict the structure evolution under short pulse HHF loads.

Contribution to the study of the creep of uranium dioxide. Role of grain growth promoters

International Nuclear Information System (INIS)

Vivant-Duguay, Christelle

1998-01-01

Improvement of nuclear fuel performances involves enhancing the plasticity of uranium dioxide UO 2 , in order to reduce the stress applied by the pellet to the cladding during a power ramp. The objective of this work is to identify and to formulate the effects produced by the nature and the concentration of additives of corundum structure, Cr 2 O 3 or Al 2 O 3 , which are grain growth promoters for UO 2 . The review of literature data establishes that oxygen content, grain size or porosity markedly affect the mechanical properties of uranium dioxide. On the other hand, there is relatively little reported work on the influence of doping. Prepared samples have been deformed by uniaxial compression. In the case of standard undoped UO 2 , two distinct preponderant creep mechanisms occur depending on stress level: a grain boundary diffusional creep, as per Coble, for stresses below the transition stress and a dislocation creep above. The doped materials have a large grained microstructure, which allows a dislocation creep only. In the range of temperature and stress investigated here, doping significantly improves the plasticity of standard UO 2 . This common effect of dopants is characterized by a decrease in the flow stress for tests with constant strain rate and by enhanced steady-state creep rates. Cr 2 O 3 doping is the more effective. The apparent benefit of doping results from the gain due to the increased grain size, but it is compensated by the strengthening effect of the additive. The creep law used to describe the behavior of standard UO 2 , has been modified to account for the influence of the dopant, by including either the concentration or the grain size. (author) [fr

CH3NH3PbI3 grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition

Science.gov (United States)

Yao, Zhibo; Wang, Wenli; Shen, Heping; Zhang, Ye; Luo, Qiang; Yin, Xuewen; Dai, Xuezeng; Li, Jianbao; Lin, Hong

2017-12-01

Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH3NH3PbI3 perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO2 (mp-TiO2)/CH3NH3PbI3/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI2 (C(PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH3NH3PbI3 grain growth phenomenon atop mesoporous TiO2 film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI2 to CH3NH3PbI3, and discuss the PbI2 nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH3NH3PbI3 grains with different morphology. These C(PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO2/CH3NH3PbI3/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH3NH3PbI3 morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs.

Fractal dust grains in plasma

International Nuclear Information System (INIS)

Huang, F.; Peng, R. D.; Liu, Y. H.; Chen, Z. Y.; Ye, M. F.; Wang, L.

2012-01-01

Fractal dust grains of different shapes are observed in a radially confined magnetized radio frequency plasma. The fractal dimensions of the dust structures in two-dimensional (2D) horizontal dust layers are calculated, and their evolution in the dust growth process is investigated. It is found that as the dust grains grow the fractal dimension of the dust structure decreases. In addition, the fractal dimension of the center region is larger than that of the entire region in the 2D dust layer. In the initial growth stage, the small dust particulates at a high number density in a 2D layer tend to fill space as a normal surface with fractal dimension D = 2. The mechanism of the formation of fractal dust grains is discussed.

HvDep1 Is a Positive Regulator of Culm Elongation and Grain Size in Barley and Impacts Yield in an Environment-Dependent Manner.

Directory of Open Access Journals (Sweden)

Toni Wendt

Full Text Available Heterotrimeric G proteins are intracellular membrane-attached signal transducers involved in various cellular processes in both plants and animals. They consist of three subunits denoted as α, β and γ. The γ-subunits of the so-called AGG3 type, which comprise a transmembrane domain, are exclusively found in plants. In model species, these proteins have been shown to participate in the control of plant height, branching and seed size and could therefore impact the harvestable yield of various crop plants. Whether AGG3-type γ-subunits influence yield in temperate cereals like barley and wheat remains unknown. Using a transgenic complementation approach, we show here that the Scottish malting barley cultivar (cv. Golden Promise carries a loss-of-function mutation in HvDep1, an AGG3-type subunit encoding gene that positively regulates culm elongation and seed size in barley. Somewhat intriguingly, agronomic field data collected over a 12-year period reveals that the HvDep1 loss-of-function mutation in cv. Golden Promise has the potential to confer either a significant increase or decrease in harvestable yield depending on the environment. Our results confirm the role of AGG3-type subunit-encoding genes in shaping plant architecture, but interestingly also indicate that the impact HvDep1 has on yield in barley is both genotypically and environmentally sensitive. This may explain why widespread exploitation of variation in AGG3-type subunit-encoding genes has not occurred in temperate cereals while in rice the DEP1 locus is widely exploited to improve harvestable yield.

A review on the factors affecting mite growth in stored grain commodities.

Science.gov (United States)

Collins, D A

2012-03-01

A thorough review of the literature has identified the key factors and interactions that affect the growth of mite pests on stored grain commodities. Although many factors influence mite growth, the change and combinations of the physical conditions (temperature, relative humidity and/or moisture content) during the storage period are likely to have the greatest impact, with biological factors (e.g. predators and commodity) playing an important role. There is limited information on the effects of climate change, light, species interactions, local density dependant factors, spread of mycotoxins and action thresholds for mites. A greater understanding of these factors may identify alternative control techniques. The ability to predict mite population dynamics over a range of environmental conditions, both physical and biological, is essential in providing an early warning of mite infestations, advising when appropriate control measures are required and for evaluating control measures. This information may provide a useful aid in predicting and preventing mite population development as part of a risk based decision support system.

Enhancement of Growth and Grain Yield of Rice in Nutrient Deficient Soils by Rice Probiotic Bacteria

Institute of Scientific and Technical Information of China (English)

Md Mohibul Alam KHAN; Effi HAQUE; Narayan Chandra PAUL; Md Abdul KHALEQUE; Saleh M. S. AL-GARNI; Mahfuzur RAHMAN; Md Tofazzal ISLAM

2017-01-01

Plant associated bacteria are promising alternatives to chemical fertilizers for plant growth and yield improvement in an eco-friendly manner. In this study, rice associated bacteria were isolated and assessed for mineral phosphate solubilization and indole-3-acetic acid (IAA) production activity in vitro. Six promising strains, which were tentatively identified as phylotaxon Pseudochrobactrum sp. (BRRh-1), Burkholderia sp. (BRRh-2), Burkholderia sp. (BRRh-3), Burkholderia sp. (BRRh-4), Pseudomonas aeruginosa (BRRh-5 and BRRh-6) based on their 16S rRNA gene phylogeny, exhibited significant phosphate solubilizing activity in National Botanical Research Institute phosphate growth medium, and BRRh-4 displayed the highest phosphate solubilizing activity, followed by BRRh-5. The pH of the culture broth declined, resulting in increase of growth rate of bacteria at pH 7, which might be due to organic acid secretion by the strains. In presence of L-tryptophan, five isolates synthesized IAA and the maximum IAA was produced by BRRh-2, followed by BRRh-1. Application of two most efficient phosphate solubilizing isolates BRRh-4 and BRRh-5 by root dipping (colonization) of seedling and spraying at the flowering stage significantly enhanced the growth and grain yield of rice variety BRRI dhan-29. Interestingly, application of both strains with 50% of recommended nitrogen, phosphorus and potassium fertilizers produced equivalent or higher grain yield of rice compared to the control grown with full recommended fertilizer doses, which suggests that these strains may have the potential to be used as bioinoculants for sustainable rice production.

Sodium induced grain growth, defect passivation and enhancement in the photovoltaic properties of Cu{sub 2}ZnSnS{sub 4} thin film solar cell

Energy Technology Data Exchange (ETDEWEB)

Singh, Om Pal; Gour, Kuldeep Singh [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Parmar, Rahul [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Singh, Vidya Nand, E-mail: singhvn@nplindia.org [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)

2016-07-01

Sodium diffusion from soda lime glass (SLG) during high temperature annealing is known to play a crucial role in affecting the grain growth and defect passivation in chalocogenide/kesterite solar cells. Additional sodium is required when low temperature or short term annealing is used. Although this fact is known, a systematic comparative study for kesterite films is seldom reported. In the present study, Cu{sub 2}ZnSnS{sub 4} thin films were deposited on SLG and Mo coated SLG using stacked layer reactive sputtering. Na was deposited over the CZTS thin film and the film was annealed in N{sub 2} atmosphere in order to enhance the grain growth. This resulted in the shift in the XRD peak towards lower diffraction angle. The optical bandgap shifted from 1.45 eV to 1.38 eV with Na addition. Significant grain growth from hundreds of nanometer to micrometer was observed in samples with Na. Device fabricated in SLG/Mo/CZTS/CdS/ZnO/ITO configuration with Al front contact shows increase in efficiencies values from 1.50% to 2.84%. - Highlights: • Reactive sputtering with reduced annealing time have been used for the growth of CZTS thin film. • NaF has been deposited over precursor film before annealing. • Na addition resulted in grain growth, improved compactness and reduction in band gap. • An enhancement in the photovoltaic characteristics have been observed with addition of Na.

Manifestations of strain–relaxation in the structure of nano-sized Co-2 × 2 islands grown on Ag/Ge(111)-√3 × √3 surface

International Nuclear Information System (INIS)

Huang, Xiao-Lan; Tomaszewska, Agnieszka; Lin, Chun-Liang; Tsay, Sung-Lin; Chou, Chi-Hao; Fu, Tsu-Yi

2012-01-01

We have examined strain–relaxation of Co-2 × 2 islands grown on the Ag/Ge(111)-√3 × √3 surface by analyzing scanning tunneling microscopy images. We have found that the Co-2 × 2 islands commonly adopt a more compact arrangement as compared to that of the Ge(111) substrate, however they differ in a degree of an atomic compactness. We have not found a distinct relation between strain–relaxation and the island height. Three groups of islands have been identified upon analyzing a correspondence between strain–relaxation and the island size: (i) small islands (not bigger than 80 nm 2 ) with a high atomic compactness, displaying fixed inter-row distances, (ii) small islands with unfixed distances between atomic rows, and (iii) big islands (bigger than 80 nm 2 ) with fixed inter-row distances, but with a less compact atomic arrangement compared to that of the first two groups. We propose a model to account for the relation between the relaxation and the island size. - Highlights: ► We examine strain–relaxation of Co-2 × 2 islands grown on Ag/Ge(111)-√3 × √3 surface. ► The Co-2 × 2 islands are more compact as compared to the substrate. ► No relation between the relaxation and the island height. ► Atomic compactness and atomic order as manifestations of strain–relaxation.

A Rare Allele of GS2 Enhances Grain Size and Grain Yield in Rice.

Science.gov (United States)

Hu, Jiang; Wang, Yuexing; Fang, Yunxia; Zeng, Longjun; Xu, Jie; Yu, Haiping; Shi, Zhenyuan; Pan, Jiangjie; Zhang, Dong; Kang, Shujing; Zhu, Li; Dong, Guojun; Guo, Longbiao; Zeng, Dali; Zhang, Guangheng; Xie, Lihong; Xiong, Guosheng; Li, Jiayang; Qian, Qian

2015-10-05

Grain size determines grain weight and affects grain quality. Several major quantitative trait loci (QTLs) regulating grain size have been cloned; however, our understanding of the underlying mechanism that regulates the size of rice grains remains fragmentary. Here, we report the cloning and characterization of a dominant QTL, grain size on chromosome 2 (GS2), which encodes Growth-Regulating Factor 4 (OsGRF4), a transcriptional regulator. GS2 localizes to the nucleus and may act as a transcription activator. A rare mutation of GS2 affecting the binding site of a microRNA, OsmiR396c, causes elevated expression of GS2/OsGRF4. The increase in GS2 expression leads to larger cells and increased numbers of cells, which thus enhances grain weight and yield. The introduction of this rare allele of GS2/OsGRF4 into rice cultivars could significantly enhance grain weight and increase grain yield, with possible applications in breeding high-yield rice varieties. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Spatial Price Discovery, Dynamics, and Leadership in Evolving Distiller’s Grain Markets

OpenAIRE

Van Winkle, Tyler W.; Schroeder, Ted C.

2008-01-01

Recent dramatic growth in corn-based bio-refining has generated considerable growth in the by-product of this process, distiller’s grains. Distiller’s grains are rapidly becoming important livestock feed ingredient sources. However, little public market information is available on distiller’s grain. This study determines spatial and temporal price relationships among distiller’s grain markets. Results indicate spatial distiller’s grain markets operate somewhat independently suggesting potenti...

Stochastic modeling of columnar dendritic grain growth in weld pool of Al-Cu alloy

Energy Technology Data Exchange (ETDEWEB)

Dong, Z.B.; Tian, N. [The State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin (China); Wei, Y.H. [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing (China); The State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin (China); Zhan, X.H.

2009-04-15

A multi-scale model is used to simulate columnar dendritic growth in TIG (tungsten inert-gas) weld molten pool of Al-Cu alloy. The grain morphologies at the edge of the weld pool are studied. The simulated results indicate that the average primary dendrite spacing changes during the solidification process in the weld pool because of the complicated thermal field, solute diffusion field and competitive growth. And it is shown that the secondary dendrite arms grow insufficiently in the space between dendrite trunks if the primary dendrite spacing is small. And the phenomenon has been explained by analyzing the influence of the solute accumulation on the constitutional undercooling and undercooling gradient when there are two different opposite solute diffusion fields. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Heating temperature effect on ferritic grain size of rotor steel

International Nuclear Information System (INIS)

Cheremnykh, V.G.; Derevyankin, E.V.; Sakulin, A.A.

1983-01-01

The heating temperature effect on ferritic grain size of two steels 13Kh1M1FA and 25Kh1M1FA is evaluated. It is shown that exposure time increase at heating temperatures below 1000 deg C up to 10h changes but slightly the size of the Cr-Mo-V ferritic grain of rotor steel cooled with 25 deg C/h rate. Heating up to 1000 deg C and above leads to substantial ferritic grain growth. The kinetics of ferritic grain growth is determined by the behaviour of phases controlling the austenitic grain growth, such as carbonitrides VCsub(0.14)Nsub(0.78) in 13Kh1M1FA steel and VCsub(0.18)Nsub(0.72) in 25Kh1M1FA steel. Reduction of carbon and alloying elements content in steel composition observed at the liquation over rotor length leads to a certain decrease of ferritic grain resistance to super heating

Effects of feeding blends of grains naturally contaminated with Fusarium mycotoxins on growth and immunological parameters of broiler chickens.

Science.gov (United States)

Swamy, H V L N; Smith, T K; Karrow, N A; Boermans, H J

2004-04-01

An experiment was conducted to investigate the effects of feeding grains naturally contaminated with Fusarium mycotoxins on growth and immunological parameters of broiler chickens. Three hundred sixty, 1-d-old male broiler chicks were fed 1 of 4 diets containing grains naturally contaminated with Fusarium mycotoxins for 56 d. The diets included (1) control; (2) low level of contaminated grains (5.9 mg/kg deoxynivalenol (DON), 19.1 mg/kg fusaric acid (FA), 0.4 mg/kg zearalenone, and 0.3 mg/kg 15-acetyldeoxynivalenol; (3) high level of contaminated grains (9.5 mg/kg DON, 21.4 mg/kg FA, 0.7 mg/kg zearalenone, and 0.5 mg/kg 15-acetyldeoxynivalenol); and (4) high level of contaminated grains + 0.2% polymeric glucomannan mycotoxin adsorbent (GM polymer). Body weight gains and feed consumption of chickens fed contaminated grains decreased linearly with the inclusion of contaminated grains during the grower phase (d 21 to 42). Efficiency of feed utilization, however, was not affected by diet. Production parameters were not significantly affected by the supplementation of GM polymer to the contaminated grains. Peripheral blood monocytes decreased linearly in birds fed contaminated grains. The feeding of contaminated diets linearly reduced the B-cell count at the end of the experiment, whereas the T-cell count on d 28 responded quadratically to the contaminated diets. The feeding of contaminated diets did not significantly alter serum or bile immunoglobulin concentrations, contact hypersensitivity to dinitrochlorobenzene, or antibody response to SRBC. Supplementation with GM polymer in the contaminated diet nonspecifically increased white blood cell count and lymphocyte count, while preventing mycotoxin-induced decreases in B-cell counts. It was concluded that broiler chickens are susceptible during extended feeding of grains naturally contaminated with Fusarium mycotoxins.

Growth, Structure and Firm Dynamics in Grain Markets: The Case of ...

African Journals Online (AJOL)

Optiplex 7010 Pro

In this paper we consider the microeconomic evidence on the determinants of firm performance in Ethiopia, with a focus on grain traders. We analyse both internal and external factors, and the relative impacts of these factors on the performance of grain traders. Different economic indicators seem to suggest that grain ...

The effect of grain refinement and silicon content on grain formation in hypoeutectic Al-Si alloys

Energy Technology Data Exchange (ETDEWEB)

Lee, Y.C.; Dahle, A.K.; StJohn, D.H.; Hutt, J.E.C. [Queensland Univ., Brisbane (Australia). Dept. of Mining, Minerals and Mater. Eng.

1999-01-15

The effect of increasing the amount of added grain refiner on grain size and morphology has been investigated for a range of hypoeutectic Al-Si alloys. The results show a transition in grain size at a silicon concentration of about 3 wt% in unrefined alloys; the grain size decreasing with silicon content before the transition, and increasing beyond the transition point. A change in morphology also occurs with increased silicon content. The addition of grain refiner leads to greater refinement for silicon contents below the transition point than for those contents above the transition point, while the transition point seems to remain unchanged. The slope of the grain size versus silicon content curve after the transition seems to be unaffected by the degree of grain refinement. The results are related to the competitive processes of nucleation and constitutional effects during growth and their impact on nucleation kinetics. (orig.) 13 refs.

Abnormal Grain Growth in the Heat Affected Zone of Friction Stir Welded Joint of 32Mn-7Cr-1Mo-0.3N Steel during Post-Weld Heat Treatment

Directory of Open Access Journals (Sweden)

Yijun Li

2018-04-01

Full Text Available The abnormal grain growth in the heat affected zone of the friction stir welded joint of 32Mn-7Cr-1Mo-0.3N steel after post-weld heat treatment was confirmed by physical simulation experiments. The microstructural stability of the heat affected zone can be weakened by the welding thermal cycle. It was speculated to be due to the variation of the non-equilibrium segregation state of solute atoms at the grain boundaries. In addition, the pressure stress in the welding process can promote abnormal grain growth in the post-weld heat treatment.

Coarse-graining and hybrid methods for efficient simulation of stochastic multi-scale models of tumour growth

Science.gov (United States)

de la Cruz, Roberto; Guerrero, Pilar; Calvo, Juan; Alarcón, Tomás

2017-12-01

The development of hybrid methodologies is of current interest in both multi-scale modelling and stochastic reaction-diffusion systems regarding their applications to biology. We formulate a hybrid method for stochastic multi-scale models of cells populations that extends the remit of existing hybrid methods for reaction-diffusion systems. Such method is developed for a stochastic multi-scale model of tumour growth, i.e. population-dynamical models which account for the effects of intrinsic noise affecting both the number of cells and the intracellular dynamics. In order to formulate this method, we develop a coarse-grained approximation for both the full stochastic model and its mean-field limit. Such approximation involves averaging out the age-structure (which accounts for the multi-scale nature of the model) by assuming that the age distribution of the population settles onto equilibrium very fast. We then couple the coarse-grained mean-field model to the full stochastic multi-scale model. By doing so, within the mean-field region, we are neglecting noise in both cell numbers (population) and their birth rates (structure). This implies that, in addition to the issues that arise in stochastic-reaction diffusion systems, we need to account for the age-structure of the population when attempting to couple both descriptions. We exploit our coarse-graining model so that, within the mean-field region, the age-distribution is in equilibrium and we know its explicit form. This allows us to couple both domains consistently, as upon transference of cells from the mean-field to the stochastic region, we sample the equilibrium age distribution. Furthermore, our method allows us to investigate the effects of intracellular noise, i.e. fluctuations of the birth rate, on collective properties such as travelling wave velocity. We show that the combination of population and birth-rate noise gives rise to large fluctuations of the birth rate in the region at the leading edge of

Secondary recrystallization in non-sag W filament wires -- On the possible role of relative grain boundary character distribution

International Nuclear Information System (INIS)

Samajdar, I.; Watte, P.; Mertens, F.

1999-01-01

Non-Sag tungsten (W) wire is indispensable for the lighting industry. For the necessary creep resistance, large elongated grains are considered as the desired microstructure. These large grains are obtained by primary and secondary recrystallization. In the present study an effort has been made to characterize and to understand the origin of such large elongated grains. In secondary recrystallization, often called abnormal grain growth, a few of the grains grow massive. The mechanisms of normal and abnormal grain growth are essentially the same, involving high angle boundary migration and driven by the reduction of surface energy. The abnormal grain growth can be visualized as a growth advantage for a few of the grains or growth disadvantage for the majority. Such an advantage/disadvantage may be caused by (1) differences in grain size and/or (2) differences in grain boundary character distribution (GBCD). In other words, a grain may grow massive if it has large size and/or possibilities of more favorable (i.e., of higher mobility) grain boundaries with the matrix grains

Effect of time and temperature on grain size of V and V-Cr-Ti alloys

International Nuclear Information System (INIS)

Natesan, K.; Rink, D.L.

1996-01-01

Grain growth studies were conducted to evaluate the effect of time and temperature on the grain size of pure V, V-4 wt.%Cr-4 wt.%Ti, and V-5 wt.%Cr-5 wt.%Ti alloys. The temperatures used in the study were 500, 650, 800, and 1000 degrees C, and exposure times ranged between 100 and ∼5000 h. All three materials exhibited negligible grain growth at 500, 650, and 800 degrees C, even after ∼5000 h. At 1000 degrees C, pure V showed substantial grain growth after only 100 h, and V-4Cr-4Ti showed growth after 2000 h, while V-5Cr-5Ti showed no grain growth after exposure for up to 2000 h

AggNet: Deep Learning From Crowds for Mitosis Detection in Breast Cancer Histology Images.

Science.gov (United States)

Albarqouni, Shadi; Baur, Christoph; Achilles, Felix; Belagiannis, Vasileios; Demirci, Stefanie; Navab, Nassir

2016-05-01

The lack of publicly available ground-truth data has been identified as the major challenge for transferring recent developments in deep learning to the biomedical imaging domain. Though crowdsourcing has enabled annotation of large scale databases for real world images, its application for biomedical purposes requires a deeper understanding and hence, more precise definition of the actual annotation task. The fact that expert tasks are being outsourced to non-expert users may lead to noisy annotations introducing disagreement between users. Despite being a valuable resource for learning annotation models from crowdsourcing, conventional machine-learning methods may have difficulties dealing with noisy annotations during training. In this manuscript, we present a new concept for learning from crowds that handle data aggregation directly as part of the learning process of the convolutional neural network (CNN) via additional crowdsourcing layer (AggNet). Besides, we present an experimental study on learning from crowds designed to answer the following questions. 1) Can deep CNN be trained with data collected from crowdsourcing? 2) How to adapt the CNN to train on multiple types of annotation datasets (ground truth and crowd-based)? 3) How does the choice of annotation and aggregation affect the accuracy? Our experimental setup involved Annot8, a self-implemented web-platform based on Crowdflower API realizing image annotation tasks for a publicly available biomedical image database. Our results give valuable insights into the functionality of deep CNN learning from crowd annotations and prove the necessity of data aggregation integration.

Determination of the growth restriction factor and grain size for aluminum alloys by a quasi-binary equivalent method

International Nuclear Information System (INIS)

Mitrašinović, A.M.; Robles Hernández, F.C.

2012-01-01

Highlights: ► A new method to determine the growth restricting factor. (Q) is proposed ► The proposed method is highly accurate (R 2 = 0.99) and simple. ► A major novelty of this method is the determination of Q for non-dilute samples. ► The method proposed herein is based on quasi-binary phase diagrams and composition. ► This method can be easily implemented industrially or as a research tool. - Abstract: In the present research paper is suggested a new methodology to determine the growth restricting factor (Q) and grain size (GS) for various Al-alloys. The present method combines a thermodynamical component based on the liquidus behavior of each alloying element that is later incorporated into the well known growth restricting models for multi-component alloys. This approach that can be used to determine Q and/or GS based on the chemical composition and the slope of the liquidus temperature of any Al-alloy solidified in close to equilibrium conditions. This method can be modified further in order to assess the effect of cooling rate or thermomechanical processing on growth restricting factor and grain size. In the present paper is proposed a highly accurate (R 2 = 0.99) and validated model for Al–Si alloys, but it can be modified for any other Al–X alloying system. The present method can be used for alloys with relatively high solute content and due to the use of the thermodynamics of liquidus this system considers the poisoning effects of single and multi-component alloying elements.

Phase transformation and grain growth behavior of a nanocrystalline 18/8 stainless steel

Energy Technology Data Exchange (ETDEWEB)

Kotan, Hasan, E-mail: hasankotan@gmail.com [Konya Necmettin Erbakan University, Department of Metallurgical & Materials Engineering, Konya 42090 (Turkey); Darling, Kris A. [US Army Research Laboratory, Weapons and Materials Research Directorate, RDRL-WMM-F, Aberdeen Proving Ground, MD 21005-5069 (United States)

2017-02-16

Fe-18Cr-8Ni and Fe-18Cr-8Ni-1Y (at%) stainless steel powders were nanostructured by mechanical alloying from elemental powders and subjected to 90 min annealing treatments at various temperatures. The microstructural evolutions as a function of alloy compositions and temperatures were investigated by in-situ and ex-situ x-ray diffraction experiments, transmission electron microscopy and focused ion beam microscopy. The dependence of hardness on the microstructure was utilized to study the mechanical changes. It was found that the resulting microstructures by mechanical alloying were bcc solid solution, the so-called α’-martensite structure. The high temperature in-situ x-ray diffraction experiments showed that the martensite-to-austenite reverse phase transformation was completed above 800 and 900 °C for Fe-18Cr-8Ni and Fe-18Cr-8Ni-1Y steels, respectively. A partial or complete retransformation to martensite was observed upon cooling to room temperature. Annealing of nanocrystalline Fe-18Cr-8Ni steel yielded grain growth reaching to micron sizes at 1100 °C while addition of 1 at% yttrium stabilized the microstructure around 160 nm grain size and 6 GPa hardness after 90 min annealing at 1200 °C.

Plant growth-promoting actinobacteria: a new strategy for enhancing sustainable production and protection of grain legumes.

Science.gov (United States)

Sathya, Arumugam; Vijayabharathi, Rajendran; Gopalakrishnan, Subramaniam

2017-06-01

Grain legumes are a cost-effective alternative for the animal protein in improving the diets of the poor in South-East Asia and Africa. Legumes, through symbiotic nitrogen fixation, meet a major part of their own N demand and partially benefit the following crops of the system by enriching soil. In realization of this sustainability advantage and to promote pulse production, United Nations had declared 2016 as the "International Year of pulses". Grain legumes are frequently subjected to both abiotic and biotic stresses resulting in severe yield losses. Global yields of legumes have been stagnant for the past five decades in spite of adopting various conventional and molecular breeding approaches. Furthermore, the increasing costs and negative effects of pesticides and fertilizers for crop production necessitate the use of biological options of crop production and protection. The use of plant growth-promoting (PGP) bacteria for improving soil and plant health has become one of the attractive strategies for developing sustainable agricultural systems due to their eco-friendliness, low production cost and minimizing consumption of non-renewable resources. This review emphasizes on how the PGP actinobacteria and their metabolites can be used effectively in enhancing the yield and controlling the pests and pathogens of grain legumes.

Comparison of alternative beef production systems based on forage finishing or grain-forage diets with or without growth promotants: 2. Meat quality, fatty acid composition, and overall palatability.

Science.gov (United States)

Faucitano, L; Chouinard, P Y; Fortin, J; Mandell, I B; Lafrenière, C; Girard, C L; Berthiaume, R

2008-07-01

Five beef cattle management regimens were evaluated for their effect on meat quality, fatty acid composition, and overall palatability of the longis-simus dorsi (LD) muscle in Angus cross steers. A 98-d growing phase was conducted using grass silage with or without supplementation of growth promotants (Revalor G and Rumensin) or soybean meal. Dietary treatments in the finishing phase were developed with or without supplementation of growth promotants based on exclusive feeding of forages with no grain supplementation, or the feeding of grain:forage (70:30) diets. Growth promotants increased (P forages increased the proportion of cis-9, cis-12, cis-15 C18:3 as well as several other isomers of the n-3 family and decreased in the ratio of n-6 to n-3 fatty acids in the LD muscle as compared with supplementing grain (P forage-based diet increased (P Forage feeding also increased the proportion of cis-9, trans-11 C18:2 (P forage-finishing and growth promotants-free beef production system.

Growth of large-size-two-dimensional crystalline pentacene grains for high performance organic thin film transistors

Directory of Open Access Journals (Sweden)

Chuan Du

2012-06-01

Full Text Available New approach is presented for growth of pentacene crystalline thin film with large grain size. Modification of dielectric surfaces using a monolayer of small molecule results in the formation of pentacene thin films with well ordered large crystalline domain structures. This suggests that pentacene molecules may have significantly large diffusion constant on the modified surface. An average hole mobility about 1.52 cm2/Vs of pentacene based organic thin film transistors (OTFTs is achieved with good reproducibility.

Interior seeding for the fabrication of single-grain REBCO bulk superconductors

International Nuclear Information System (INIS)

Kim, C-J; Park, S-D; Jun, B-H; Park, H-W

2016-01-01

This study presents a new seeding technique, named ‘interior seeding’ which allows the growth of a single REBCO (RE: rare-earth elements) grain in the interior of REBCO compacts. The key techniques of interior seeding are to provide appropriate open space for seeds in the interior of REBCO powder compacts to supply air or oxygen to the seeds, and to minimize the contact area between the seeds and liquid. The advantages of interior seeding are as follows: (1) simultaneous growth from the seed to the top and bottom of the REBCO compacts is possible, (2) fractions of the a-b growth sector and the a-c growth sector on the top surface can be controlled and (3) the top surfaces of the single-grain REBCO bulk superconductors are free from samarium or neodymium contamination from the used seeds. The very large single-grain Y 1.5 Ba 2 Cu 3 O 7−y (Y1.5) bulk superconductors (42 mm) were successfully fabricated using a melt growth (MG) process combined with interior seeding. Also, large-grain Y1.5 bulk superconductors (41 mm) with 〈110〉/〈110〉 and 〈100〉/〈100〉 grain junctions were fabricated using multiple interior seeding. In this paper, the detailed process of interior seeding, the development of top surface patterns and the properties of single-grain Y123 bulk superconductors fabricated using interior seeding were reported. (paper)

The effect of the Tom Thumb dwarfing gene on grain size and grain number of wheat (Triticum aestivum)

International Nuclear Information System (INIS)

Gale, M.D.; Flintham, J.E.

1984-01-01

The Tom Thumb dwarfing gene, Rht3, like the related genes Rht1 and Rht2 from Norin 10, has pleiotropic effects on individual ear yields, and grain protein concentrations. An experiment was conducted in which tiller number per plant and grain number per spike were restricted to ascertain whether reduced grain size and protein content are primary or secondary competitive effects in near-isogenic lines. The potential for grain growth was shown to be identical in Rht3 and rht genotypes when grain set was restricted, indicating that the primary effect of the gene is to increase spikelet fertility. Nitrogen accumulation within the grain was also affected by inter-grain competition but decreased nitrogen yields per plant indicated that reduced protein levels are, in part, a primary effect of the gene. Analysis of individual grain yields within Rht3 and rht spikes showed that the gene affected developmental 'dominance' relationships within the spike. (author)

The effect of secondary abnormal grain growth on the dielectric properties of La/Mn co-doped BaTiO3 ceramics

Directory of Open Access Journals (Sweden)

Živković Lj.M.

2006-01-01

Full Text Available La/Mn-codoped BaTiO3 systems, obtained by solid state reactions, were investigated regarding their microstructure characteristics and ferroelectric properties. Different concentrations of La2O3 were used for doping, ranging from 0.1 to 5.0 at% La, while a content of Mn was constant at 0.05 at%. For all samples sintered below the eutectic temperature (1332°C, a uniform microstructure was formed with average grain size from 1-3 μm. The appearance of secondary abnormal grains with (111 double twins grains with curved or faceted grain boundaries were observed in La/Mn BaTiO3 ceramics after sintering at temperatures above the eutectic temperature. All sintered samples exhibited a high electrical resistivity. Better dielectric performances were obtained for low doped samples (0.1 at% La sintered at 1350°C. For samples with La content above 1.0 at% a lower value in dielectric permittivity at higher sintering temperature is due to secondary abnormal grain growth, and to the presence of a non-ferroelectric phase rich in La. The Curie constant together with other dielectric parameters were also calculated.

Behavior of Goss, {411}<148>, and {111}<112> Oriented Grains During Recrystallization and Decarburization After Cold-rolling of Fe-3.1% GrainOriented Electrical Steel

Energy Technology Data Exchange (ETDEWEB)

Choi, Sung-Ji; Park, No-Jin [Kumoh National Institute of Technology, Gumi (Korea, Republic of); Joo, Hyung-Don; Park, Jong-Tae [POSCO, Pohang (Korea, Republic of)

2016-07-15

Grain-oriented electrical steel is used as a core material in transformers and motors. To obtain improved magnetic properties from the grain-oriented electrical steel, the steel should have a strong {110}<001> Goss texture. Recently, controlled manufacturing processes have been employed for developing electrical steels with a strong Goss texture. It is important to carry out research on the {411}<148> and {111}<112> oriented grains in relation to coincidence site lattice (CSL) boundaries, as they have an effect on the easy growth of the Goss grains upon secondary recrystallization. In this study, the behavior of the{411}<148> and {111}<112> oriented grains, which are neighbored with Goss grains after recrystallization with rapid and typical heating rates, and after decarburization, was examined by using x-ray diffraction (XRD) and electron back-scattered diffraction (EBSD) measurements. In the decarburized specimen, the Goss grains encroached the {411}<148> and {111}<112> oriented grains to a greater extent with a rapid heating rate than with a typical heating rate, and larger Goss grains were observed with the rapid heating rate. The {111}<112> oriented grains especially affect the easy growth of the Goss grains, as they are located near the Goss grains. Therefore, larger Goss grains can be produced at rapid heating rates, and the product is estimated to exhibit improved magnetic properties after secondary recrystallization.

INFRARED SPECTROSCOPIC SURVEY OF THE QUIESCENT MEDIUM OF NEARBY CLOUDS. I. ICE FORMATION AND GRAIN GROWTH IN LUPUS

International Nuclear Information System (INIS)

Boogert, A. C. A.; Chiar, J. E.; Knez, C.; Mundy, L. G.; Öberg, K. I.; Pendleton, Y. J.; Tielens, A. G. G. M.; Van Dishoeck, E. F.

2013-01-01

Infrared photometry and spectroscopy (1-25 μm) of background stars reddened by the Lupus molecular cloud complex are used to determine the properties of grains and the composition of ices before they are incorporated into circumstellar envelopes and disks. H 2 O ices form at extinctions of A K = 0.25 ± 0.07 mag (A V = 2.1 ± 0.6). Such a low ice formation threshold is consistent with the absence of nearby hot stars. Overall, the Lupus clouds are in an early chemical phase. The abundance of H 2 O ice (2.3 ± 0.1 × 10 –5 relative to N H ) is typical for quiescent regions, but lower by a factor of three to four compared to dense envelopes of young stellar objects. The low solid CH 3 OH abundance ( 2 O) indicates a low gas phase H/CO ratio, which is consistent with the observed incomplete CO freeze out. Furthermore it is found that the grains in Lupus experienced growth by coagulation. The mid-infrared (>5 μm) continuum extinction relative to A K increases as a function of A K . Most Lupus lines of sight are well fitted with empirically derived extinction curves corresponding to R V ∼ 3.5 (A K = 0.71) and R V ∼ 5.0 (A K = 1.47). For lines of sight with A K > 1.0 mag, the τ 9.7 /A K ratio is a factor of two lower compared to the diffuse medium. Below 1.0 mag, values scatter between the dense and diffuse medium ratios. The absence of a gradual transition between diffuse and dense medium-type dust indicates that local conditions matter in the process that sets the τ 9.7 /A K ratio. This process is likely related to grain growth by coagulation, as traced by the A 7.4 /A K continuum extinction ratio, but not to ice mantle formation. Conversely, grains acquire ice mantles before the process of coagulation starts

3D studies of coarserning kinetics of individual grains

DEFF Research Database (Denmark)

Poulsen, Stefan Othmar

Techniques for fast, non-destructive characterization of the microstructure of materials using synchrotron X-ray radiation have in recent years become an important tool in materials science. The non-destructive nature of the techniques allows for time-resolved characterization of three-dimensiona......Techniques for fast, non-destructive characterization of the microstructure of materials using synchrotron X-ray radiation have in recent years become an important tool in materials science. The non-destructive nature of the techniques allows for time-resolved characterization of three......-dimensional microstructures, i.e. direct probing of the evolution of specific microstructural features. Synchrotron X-ray radiation techniques have in the present work been employed for experimental characterization of microstructural evolution in individual grains during isothermal annealing: For a study of individual...... grains during recrystallization, where the recrystallization kinetics of individual grains and the temperature dependence of the recrystallization rate is examined, and for a study of grain structure and grain growth, where growth predictions are put forth in terms of the grain size and topology...

Whole-plant dynamic system of nitrogen use for vegetative growth and grain filling in rice plants (Oryza sativa L. as revealed through the production of 350 grains from a germinated seed over 150 days: a review and synthesis

Directory of Open Access Journals (Sweden)

Tadakatsu Yoneyama

2016-08-01

Full Text Available A single germinated rice (Oryza sativa L seed can produce 350 grains with the sequential development of 15 leaves on the main stem and 7 ‒ 10 leaves on 4 productive tillers (forming 5 panicles in total, using nitrogen (N taken up from the environment over a 150-day growing season. Nitrogen travels from uptake sites to the grain through growing organ-directed cycling among sequentially developed organs. Over the past 40 years, the dynamic system for N allocation during vegetative growth and grain filling has been elucidated through studies on N and 15N transport as well as enzymes and transporters involved. In this review, we synthesize the information obtained in these studies along the following main points: (1 During vegetative growth before grain-filling, about half of the total N in the growing organs, including young leaves, tillers, root tips and differentiating panicles is supplied via phloem from mature source organs such as leaves and roots, after turnover and remobilization of proteins, whereas the other half is newly taken up and supplied via xylem, with an efficient xylem-to-phloem transfer at stem nodes. Thus, the growth of new organs depends equally on both N sources. (2 A large fraction (as much as 80% of the grain N is derived largely from mature organs such as leaves and stems by degradation, including the autophagy pathway of chloroplast proteins (e.g., Rubisco. (3 Mobilized proteinogenic amino acids, including arginine, lysine, proline and valine, are derived mainly from protein degradation, with amino acid transporters playing a role in transferring these amino acids across cell membranes of source and sink organs, and enabling their efficient reutilization in the latter. On the other hand, amino acids such as glutamine, glutamic acid, γ-amino butyric acid, aspartic acid, and alanine are produced by assimilation of newly taken up N by roots and transported via xylem and phloem. The formation of 350 filled grains over 50

Effect of Plant Essential Oils and Gamma Irradiation on Growth and Aflatoxin Production by Aspergillus Flavus Isolated from Wheat Grains

International Nuclear Information System (INIS)

Salem, E.A.; Shalaby, Kh.

2016-01-01

The antifungal potential of essential oils of Thyme (Thymus vulgaris L.) and camphor ( Eucalyptus rostrata L.) was determined on Aspergillus flavus link isolated from wheat grains on Potato dextrose agar (PDA). They inhibited completely mycelia growth of the fungus at 1000 and 2000 ppm, and prevented aflatoxin production at sub lethal dose 500 and 1000 ppm respectively. Gamma radiation was used to control mycelia growth of Aspergillus flavus Link and inhibiting aflatoxin production. A dose level of 3.5 KGy gamma radiation prevented the fungal growth and aflatoxin production by A. flavus link, where a dose of 2.5 K Gy ( the sub lethal dose) prevented about 85% of aflatoxin production

Role of high microwave power on growth and microstructure of thick nanocrystalline diamond films: A comparison with large grain polycrystalline diamond films

Science.gov (United States)

Tang, C. J.; Fernandes, A. J. S.; Girão, A. V.; Pereira, S.; Shi, Fa-Nian; Soares, M. R.; Costa, F.; Neves, A. J.; Pinto, J. L.

2014-03-01

In this work, we study the growth habit of nanocrystalline diamond (NCD) films by exploring the very high power regime, up to 4 kW, in a 5 kW microwave plasma chemical vapour deposition (MPCVD) reactor, through addition of a small amount of nitrogen and oxygen (0.24%) into 4% CH4 in H2 plasma. The coupled effect of high microwave power and substrate temperature on NCD growth behaviour is systematically investigated by varying only power, while fixing the remaining operating parameters. When the power increases from 2 kW to 4 kW, resulting also in rise of the Si substrate temperature higher than 150 °C, the diamond films obtained maintain the NCD habit, while the growth rate increases significantly. The highest growth rate of 4.6 μm/h is achieved for the film grown at 4 kW, which represents a growth rate enhancement of about 15 times compared with that obtained when using 2 kW power. Possible factors responsible for such remarkable growth rate enhancement of the NCD films are discussed. The evolution of NCD growth characteristics such as morphology, microstructure and texture is studied by growing thick films and comparing it with that of large grain polycrystalline (PCD) films. One important characteristic of the NCD films obtained, in contrast to PCD films, is that irrespective of deposition time (i.e. film thickness), their grain size and surface roughness remain in the nanometer range throughout the growth. Finally, based on our present and previous experimental results, a potential parameter window is established for fast growth of NCD films under high power conditions.

Grain boundary selective oxidation and intergranular stress corrosion crack growth of high-purity nickel binary alloys in high-temperature hydrogenated water

Energy Technology Data Exchange (ETDEWEB)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.; Schreiber, D. K.

2018-02-01

The effects of alloying elements in Ni-5at%X binary alloys on intergranular (IG) corrosion and stress corrosion cracking (SCC) have been assessed in 300-360°C hydrogenated water at the Ni/NiO stability line. Alloys with Cr or Al additions exhibited grain boundary oxidation and IGSCC, while localized degradation was not observed for pure Ni, Ni-Cu or Ni-Fe alloys. Environment-enhanced crack growth was determined by comparing the response in water and N2 gas. Results demonstrate that selective grain boundary oxidation of Cr and Al promoted IGSCC of these Ni alloys in hydrogenated water.

Grain-size distributions and grain boundaries of chalcopyrite-type thin films

International Nuclear Information System (INIS)

Abou-Ras, D.; Schorr, S.; Schock, H.W.

2007-01-01

CuInSe 2 , CuGaSe 2 , Cu(In,Ga)Se 2 and CuInS 2 thin-film solar absorbers in completed solar cells were studied in cross section by means of electronbackscatter diffraction. From the data acquired, grain-size distributions were extracted, and also the most frequent grain boundaries were determined. The grain-size distributions of all chalcopyrite-type thin films studied can be described well by lognormal distribution functions. The most frequent grainboundary types in these thin films are 60 - left angle 221 right angle tet and 71 - left angle 110 right angle tet (near) Σ3 twin boundaries. These results can be related directly to the importance of {112} tet planes during the topotactical growth of chalcopyrite-type thin films. Based on energetic considerations, it is assumed that the most frequent twin boundaries exhibit a 180 - left angle 221 right angle tet constellation. (orig.)

Fenton process-affected transformation of roxarsone in paddy rice soils: Effects on plant growth and arsenic accumulation in rice grain.

Science.gov (United States)

Qin, Junhao; Li, Huashou; Lin, Chuxia

2016-08-01

Batch and greenhouse experiments were conducted to examine the effects of Fenton process on transformation of roxarsone in soils and its resulting impacts on the growth of and As uptake by a rice plant cultivar. The results show that addition of Fenton reagent markedly accelerated the degradation of roxarsone and produced arsenite, which was otherwise absent in the soil without added Fenton reagent. Methylation of arsenate was also enhanced by Fenton process in the earlier part of the experiment due to abundant supply of arsenate from Roxarsone degradation. Overall, addition of Fenton reagent resulted in the predominant presence of arsenate in the soils. Fenton process significantly improved the growth of rice in the maturity stage of the first crop, The concentration of methylated As species in the rice plant tissues among the different growth stages was highly variable. Addition of Fenton reagent into the soils led to reduced uptake of soil-borne As by the rice plants and this had a significant effect on reducing the accumulation of As in rice grains. The findings have implications for understanding As biogeochemistry in paddy rice field receiving rainwater-borne H2O2 and for development of mitigation strategies to reduce accumulation of As in rice grains. Copyright © 2016 Elsevier Inc. All rights reserved.

The proportion of nitrate in leaf nitrogen, but not changes in root growth, are associated with decreased grain protein in wheat under elevated [CO2].

Science.gov (United States)

Bahrami, Helale; De Kok, Luit J; Armstrong, Roger; Fitzgerald, Glenn J; Bourgault, Maryse; Henty, Samuel; Tausz, Michael; Tausz-Posch, Sabine

2017-09-01

The atmospheric CO 2 concentration ([CO 2 ]) is increasing and predicted to reach ∼550ppm by 2050. Increasing [CO 2 ] typically stimulates crop growth and yield, but decreases concentrations of nutrients, such as nitrogen ([N]), and therefore protein, in plant tissues and grains. Such changes in grain composition are expected to have negative implications for the nutritional and economic value of grains. This study addresses two mechanisms potentially accountable for the phenomenon of elevated [CO 2 ]-induced decreases in [N]: N uptake per unit length of roots as well as inhibition of the assimilation of nitrate (NO 3 - ) into protein are investigated and related to grain protein. We analysed two wheat cultivars from a similar genetic background but contrasting in agronomic features (Triticum aestivum L. cv. Scout and Yitpi). Plants were field-grown within the Australian Grains Free Air CO 2 Enrichment (AGFACE) facility under two atmospheric [CO 2 ] (ambient, ∼400ppm, and elevated, ∼550ppm) and two water treatments (rain-fed and well-watered). Aboveground dry weight (ADW) and root length (RL, captured by a mini-rhizotron root growth monitoring system), as well as [N] and NO 3 - concentrations ([NO 3 - ]) were monitored throughout the growing season and related to grain protein at harvest. RL generally increased under e[CO 2 ] and varied between water supply and cultivars. The ratio of total aboveground N (TN) taken up per RL was affected by CO 2 treatment only later in the season and there was no significant correlation between TN/RL and grain protein concentration across cultivars and [CO 2 ] treatments. In contrast, a greater percentage of N remained as unassimilated [NO 3 - ] in the tissue of e[CO 2 ] grown crops (expressed as the ratio of NO 3 - to total N) and this was significantly correlated with decreased grain protein. These findings suggest that e[CO 2 ] directly affects the nitrate assimilation capacity of wheat with direct negative implications

Grain boundaries of nanocrystalline materials - their widths, compositions, and internal structures

International Nuclear Information System (INIS)

Fultz, B.; Frase, H.N.

2000-01-01

Nanocrystalline materials contain many atoms at and near grain boundaries. Sufficient numbers of Moessbauer probe atoms can be situated in grain boundary environments to make a clear contribution to the measured Moessbauer spectrum. Three types of measurements on nanocrystalline materials are reported here, all using Moessbauer spectrometry in conjunction with X-ray diffractometry, transmission electron microscopy, or small angle neutron scattering. By measuring the fraction of atoms contributing to the grain boundary component in a Moessbauer spectrum, and by knowing the grain size of the material, it is possible to deduce the average width of grain boundaries in metallic alloys. It is found that these widths are approximately 0.5 nm for fcc alloys and slightly larger than 1.0 nm for bcc alloys.Chemical segregation to grain boundaries can be measured by Moessbauer spectrometry, especially in conjunction with small angle neutron scattering. Such measurements on Fe-Cu and Fe 3 Si-Nb were used to study how nanocrystalline materials could be stabilized against grain growth by the segregation of Cu and Nb to grain boundaries. The segregation of Cu to grain boundaries did not stabilize the Fe-Cu alloys against grain growth, since the grain boundaries were found to widen and accept more Cu atoms during annealing. The Nb additions to Fe 3 Si did suppress grain growth, perhaps because of the low mobility of Nb atoms, but also perhaps because Nb atoms altered the chemical ordering in the alloy.The internal structure of grain boundaries in nanocrystalline materials prepared by high-energy ball milling is found to be unstable against internal relaxations at low temperatures. The Moessbauer spectra of the nanocrystalline samples showed changes in the hyperfine fields attributable to movements of grain boundary atoms. In conjunction with SANS measurements, the changes in grain boundary structure induced by cryogenic exposure and annealing at low temperature were found to be

Replacement of mineral fertilizers with anaerobically digested pig slurry in paddy fields: assessment of plant growth and grain quality.

Science.gov (United States)

Zhang, Jin; Wang, Minyan; Cao, Yucheng; Liang, Peng; Wu, Shengchun; Leung, Anna Oi Wah; Christie, Peter

2017-04-01

Rice cultivation requires large quantities of irrigation water and mineral fertilizers. This provides an opportunity for the recycling of the plant nutrients in anaerobically digested pig slurry, large amounts of which are generated in Chinese pig farms. Hence, to promote the sustainable development of livestock and poultry breeding and rice production, a micro-plot field experiment was carried out to assess whether or not slurry can replace mineral fertilizers in rice paddy production in terms of plant tillering, grain quality, and yields. The results indicate that the total N content of the slurry can serve as an alternative source of N when compared to the control (450 kg ha -1 commercial compound fertilizer (N/P 2 O 5 /K 2 O = 15:15:15) as basal fertilizer, 300 kg ha -1 urea (N% = 46), and 150 kg ha -1 commercial compound fertilizer as top-dressed fertilizer). No negative effects on plant growth or grain yield were observed, although there may be a potential risk due to an increase in grain Cu concentration. The amylose content and gel consistency of the rice grains were enhanced significantly by the use of slurry as a basal fertilizer, but the grain protein and total amino acid contents decreased. The results suggest that anaerobically digested pig slurry can replace mineral fertilizers in rice production when applied as a basal dressing together with urea and commercial compound fertilizer as top-dressed fertilizers.

Responses of Rapid Viscoanalyzer Profile and Other Rice Grain Qualities to Exogenously Applied Plant Growth Regulators under High Day and High Night Temperatures.

Directory of Open Access Journals (Sweden)

Shah Fahad

Full Text Available High-temperature stress degrades the grain quality of rice; nevertheless, the exogenous application of plant growth regulators (PGRs might alleviate the negative effects of high temperatures. In the present study, we investigated the responses of rice grain quality to exogenously applied PGRs under high day temperatures (HDT and high night temperatures (HNT under controlled conditions. Four different combinations of ascorbic acid (Vc, alpha-tocopherol (Ve, brassinosteroids (Br, methyl jasmonates (MeJA and triazoles (Tr were exogenously applied to two rice cultivars (IR-64 and Huanghuazhan prior to the high-temperature treatment. A Nothing applied Control (NAC was included for comparison. The results demonstrated that high-temperature stress was detrimental for grain appearance and milling qualities and that both HDT and HNT reduced the grain length, grain width, grain area, head rice percentage and milled rice percentage but increased the chalkiness percentage and percent area of endosperm chalkiness in both cultivars compared with ambient temperature (AT. Significantly higher grain breakdown, set back, consistence viscosity and gelatinization temperature, and significantly lower peak, trough and final viscosities were observed under high-temperature stress compared with AT. Thus, HNT was more devastating for grain quality than HDT. The exogenous application of PGRs ameliorated the adverse effects of high temperature in both rice cultivars, and Vc+Ve+MejA+Br was the best combination for both cultivars under high temperature stress.

Effect of the New Plant Growth Biostimulants Based on Amino Acids on Yield and Grain Quality of Winter Wheat.

Science.gov (United States)

Popko, Małgorzata; Michalak, Izabela; Wilk, Radosław; Gramza, Mateusz; Chojnacka, Katarzyna; Górecki, Henryk

2018-02-21

Field and laboratory experiments were carried out in 2012-2013, aimed at evaluating the influence of new products stimulating plant growth based on amino acids on crop yield, characteristics of grain and content of macro- and micronutrients in winter wheat ( Triticum aestivum L.). The tests included two formulations produced in cooperation with INTERMAG Co. (Olkusz, Poland)-AminoPrim and AminoHort, containing 15% and 20% amino acids, respectively, and 0.27% and 2.1% microelements, respectively. Field experiments showed that the application of products based on amino acids influenced the increase of grain yield of winter wheat (5.4% and 11%, respectively, for the application of AminoPrim at a dose 1.0 L/ha and AminoHort at dose 1.25 L/ha) when compared to the control group without biostimulant. Laboratory tests showed an increase of technological characteristics of grain such as ash content, Zeleny sedimentation index and content of protein. The use of the tested preparations at different doses also contributed to the increase of the nutrients content in grains, in particular copper (ranging 31-50%), as well as sodium (35-43%), calcium (4.3-7.9%) and molybdenum (3.9-16%). Biostimulants based on amino acids, tested in the present study, can be recommended for an efficient agricultural production.

Fine-grained zirconium-base material

Science.gov (United States)

Van Houten, G.R.

1974-01-01

A method is described for making zirconium with inhibited grain growth characteristics, by the process of vacuum melting the zirconium, adding 0.3 to 0.5% carbon, stirring, homogenizing, and cooling. (Official Gazette)

Fabrication and electrical properties of textured strontium(0.53)barium(0.47)niobium(2)oxygen(6) ceramics prepared by templated grain growth

Science.gov (United States)

Duran, Cihangir

Sr0.53Ba0.47Nb2O6 (SBN53) ceramics were textured by the templated grain growth (TGG), in a matrix of SrNb2O6 and BaNb2O6 powders. Acicular KSr2Nb5O15 (KSN) template particles, synthesized by a molten salt process, were used to texture the samples in the c direction (i.e., [001]). Template growth was assisted by adding V2O5 as a liquid phase former for some compositions. The texture fraction also increased with higher sintering temperatures or times and with initial template concentration due to the preferential growth of the template particles. When V2O5 was present, SBN53 phase formation initiated on the KSN templates and texture development started at temperatures as low as 950°C. Phase formation in the V2O5-free samples, however, initiated in the matrix (i.e., independent of the KSN templates). The liquid phase adversely affected the template growth by favoring anisotropic grain growth in the matrix, which caused lower texture fraction and broader texture distribution in [001] at low template concentrations. Increased template-template interaction (e.g., tangling) during tape casting also resulted in broader texture distribution. Therefore, an optimum template content was found to be ˜10--15 wt%. However, a texture fraction of 0.93 to 0.98 was obtained using only 5 wt% templates when anisotropic matrix grain growth was prevented. Phase evolution was studied in the randomly oriented samples as a function of quenching temperature, heating rate, and liquid phase, using KSN powder (rather than acicular particles) as a seed material. The formation temperature for SBN53 was lowered substantially by adding more seeds, decreasing the heating rate, and introducing a liquid. The temperature decreased from 1260°C for the samples with no seeds to 1130°C for the samples with 15.4 wt% seeds + 0.8 mol% V2O5 at a heating rate of 4°C/min. For the V2O5-free samples, the activation energy was considerably lowered from 554 +/- 15 kJ/mol for the samples with no seeds to 241

The effect of humic substances on germination and early growth of Lamb's Quarters (Chenopodium album agg.)

Czech Academy of Sciences Publication Activity Database

Šerá, Božena; Novák, František

2011-01-01

Roč. 66, č. 3 (2011), s. 470-476 ISSN 0006-3088 Institutional research plan: CEZ:AV0Z60870520; CEZ:AV0Z60660521 Keywords : Chenopodium album * growth stimulation * humic substance * lignite * seed germination Subject RIV: EH - Ecology, Behaviour Impact factor: 0.557, year: 2011

An analytical approach to elucidate the mechanism of grain refinement in calcium added Mg-Al alloys

International Nuclear Information System (INIS)

Nagasivamuni, B.; Ravi, K.R.

2015-01-01

Highlights: • Minor additions of Ca (<0.2%) refines the grain structure in Mg-(3, 6 and 9)Al alloys. • Analytical model elucidate that nucleation potency is enhanced after Ca addition. • Ternary Mg-Al-xCa growth restriction values (Q t ) are computed using Scheil equations. • Grain size predictions elucidate that nucleation events dominate grain refinement. • Growth restriction due to the higher Ca addition on grain refinement is not significant. - Abstract: The present study investigates the grain refinement of Mg-3Al, Mg-6Al and Mg-9Al alloys by calcium addition. The maximum reduction in grain size has been observed at 0.2% Ca addition in Mg-Al alloys, in which any further addition (up to 0.4%) has marginal improvement in grain refinement. The mechanism associated with the grain refinement of Mg-Al alloys by Ca addition is discussed in terms of growth restriction factor (Q) and constitutional undercooling (ΔT CS ) using analytical model. The influence of growth restriction factor (Q) on the final grain size of Ca-added Mg-Al alloys are calculated with the help analytical model by assuming that the number of nucleant particles is not altered through Ca addition. For accurate grain size calculations, the value of Q has been estimated with reliable thermodynamic database using Scheil solidification simulation. The comparison of predicted and experimental grain size results indicate that constitutional undercooling activation of nucleation events plays dominant role in grain refinement in Mg-Al alloys by calcium addition, whereas the increase in growth restriction value has negligible effect

Accumulation and conversion of sugars by developing wheat grains. VII. Effect of changes in sieve tube and endosperm cavity sap concentrations on the grain filling rate

International Nuclear Information System (INIS)

Fisher, D.B.; Gifford, R.M.

1987-01-01

The extent to which wheat grain growth is dependent on transport pool solute concentration was investigated by the use of illumination and partial grain removal to vary solute concentrations in the sieve tube and endosperm cavity saps of the wheat ear (Triticum aestivum L.). Short-term grain growth rates were estimated indirectly from the product of phloem area, sieve tube sap concentration, and 32 P translocation velocity. On a per grain basis, calculated rates of mass transport through the peduncle were fairly constant over a substantial range in other transport parameters (i.e. velocity, concentration, phloem area, and grain number). The rates were about 40% higher than expected; this probably reflects some unavoidable bias on faster-moving tracer in the velocity estimates. Sieve tube sap concentration increased in all experiments (by 20 to 64%), with a concomitant decline in velocity (to as low as 8% of the initial value). Endosperm cavity sucrose concentration also increased in all experiments, but cavity sap osmolality and total amino acid concentration remained nearly constant. No evidence was found for an increase in the rate of mass transport per grain through the peduncle in response to the treatments. This apparent unresponsiveness of grain growth rate to increased cavity sap sucrose concentration conflicts with earlier in vitro endosperm studies showing that sucrose uptake increased with increasing external sucrose concentration up to 150 to 200 millimolar

The influence of slow cooling on Y211 size and content in single-grain YBCO bulk superconductor through the infiltration-growth process

Energy Technology Data Exchange (ETDEWEB)

Ouerghi, A [Systems and Applied Mechanics Laboratory LASMAP, Polytechnic School of Tunisia, Rue El Kawarezmi La Marsa 743, Université de Carthage Tunis (Tunisia); Moutalbi, N., E-mail: nahed.moutalbi@yahoo.fr [Systems and Applied Mechanics Laboratory LASMAP, Polytechnic School of Tunisia, Rue El Kawarezmi La Marsa 743, Université de Carthage Tunis (Tunisia); Noudem, J.G. [CRISMAT-ENSICAEN (UMR-CNRS 6508), Université de Caen-Basse-Normandie, F-14050 Caen (France); LUSAC, Université de Caen-Basse-Normandie F-50130 Cherbourg-Octeville (France); M' chirgui, A. [Systems and Applied Mechanics Laboratory LASMAP, Polytechnic School of Tunisia, Rue El Kawarezmi La Marsa 743, Université de Carthage Tunis (Tunisia)

2017-03-15

Highlights: • YBCO bulk superconductors are produced by optimized Seeded Infiltration and Growth process. • The slow cooling time, in a fixed slow cooling temperature window, affects considerably the surface morphology and the bulk’s microstructure. • The Y211 particle’s size and content depend on the slow cooling time and its distribution behavior changes from one position to another. • There is an optimum slow cooling time, estimated to 88h, over which the shrinkage for both the liquid phase and the Y211 pellet is maximal, without any improvement of the crystal grain growth. • The magnetic trapped flux distribution for a given sample brings out the single grain characteristic. - Abstract: Highly textured YBa{sub 2}Cu{sub 3}O{sub 7-δ} (Y123) superconductors were produced using modified Textured Top Seeded Infiltration Growth (TSIG) process. The liquid source is made of only Y123 powder whereas the solid source is composed of Y{sub 2}BaCuO{sub 5} (Y211) powder. We aim to control the amount of liquid that infiltrates the solid pellet, which in turn controls the final amount of Y{sub 2}BaCuO{sub 5} particles in Y123 matrix. The effect of the slow cooling kinetics on sample morphology, on grain growth and on final microstructure was too investigated. It is shown that appropriate slow cooling time may also contribute to the control of the amount of Y211 inclusions in the final structure of Y123 bulk. We report herein the Y211 particle size and density distribution in the whole Y123 matrix. The present work proves that finest Y211 particles locate under the seed and that their size and density increase with distance from the seed.

SMALL GRAIN 1, which encodes a mitogen-activated protein kinase kinase 4, influences grain size in rice.

Science.gov (United States)

Duan, Penggen; Rao, Yuchun; Zeng, Dali; Yang, Yaolong; Xu, Ran; Zhang, Baolan; Dong, Guojun; Qian, Qian; Li, Yunhai

2014-02-01

Although grain size is one of the most important components of grain yield, little information is known about the mechanisms that determine final grain size in crops. Here we characterize rice small grain1 (smg1) mutants, which exhibit small and light grains, dense and erect panicles and comparatively slightly shorter plants. The short grain and panicle phenotypes of smg1 mutants are caused by a defect in cell proliferation. The smg1 mutations were identified, using a map-based cloning approach, in mitogen-activated protein kinase kinase 4 (OsMKK4). Relatively higher expression of OsMKK4/SMG1 was detected in younger organs than in older ones, consistent with its role in cell proliferation. Green fluorescent protein (GFP)-OsMKK4/SMG1 fusion proteins appear to be distributed ubiquitously in plant cells. Further results revealed that OsMKK4 influenced brassinosteroid (BR) responses and the expression of BR-related genes. Thus, our findings have identified OsMKK4 as a factor for grain size, and suggest a possible link between the MAPK pathways and BRs in grain growth. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

Columnar grain growth of FePt(L10) thin films

International Nuclear Information System (INIS)

Yang En; Ho Hoan; Laughlin, David E.; Zhu Jiangang

2012-01-01

An experimental approach for obtaining perpendicular FePt-SiOx thin films with a large height to diameter ratio FePt(L1 0 ) columnar grains is presented in this work. The microstructure for FePt-SiOx composite thin films as a function of oxide volume fraction, substrate temperature, and film thickness is studied by plan view and cross section TEM. The relations between processing, microstructure, epitaxial texture, and magnetic properties are discussed. By tuning the thickness of the magnetic layer and the volume fraction of oxide in the film at a sputtering temperature of 410 deg. C, a 16 nm thick perpendicular FePt film with ∼8 nm diameter of FePt grains was obtained. The height to diameter ratio of the FePt grains was as large as 2. Ordering at lower temperature can be achieved by introducing a Ag sacrificial layer.

Growth performance and total tract nutrient digestion for Holstein heifers limit-fed diets high in distillers grains with different forage particle sizes

Science.gov (United States)

This study evaluated dairy heifer growth performance and total tract nutrient digestion when fed diets high in dried distillers grains with solubles (DDGS) with different forage particle size. An 8-wk randomized complete block design study was conducted utilizing twenty-two Holstein heifers (123 ±...

Proteomics analysis of maize (Zea mays L.) grain based on iTRAQ reveals molecular mechanisms of poor grain filling in inferior grains.

Science.gov (United States)

Yu, Tao; Li, Geng; Liu, Peng; Dong, Shuting; Zhang, Jiwang; Zhao, Bin

2017-06-01

In maize, inferior grains (IG) located on the upper part of the ear have poor grain filling process compared to superior grains (SG) located on the middle and lower parts of the ear. This difference limits satisfactory yield and quality; however, the underlying molecular mechanisms remain unknown. Here, using the isobaric tag for relative and absolute quantification (iTRAQ) technology, the proteomes of IG and SG during early and middle grain filling stages were investigated. In total, 4720 proteins were identified in maize grain and 305 differentially accumulated proteins (DiAPs) were detected between IG and SG. These DiAPs were involved in diverse cellular and metabolic processes with preferred distribution in protein synthesis/destination and metabolism. Compared to SG, DiAPs related to cell growth/division and starch synthesis were lag-accumulated and down-regulated in IG, respectively, resulting in smaller sink sizes and lower sink activities in IG. Meanwhile, impediment of the glycolysis pathway in IG may lead to reduce energy supply and building materials for substance synthesis. Additionally, reactive oxygen species (ROS) homeostasis and the defense system were disturbed in IG, which might lead to reduce protection against various environmental stresses. The present study provides new information on the proteomic differences between IG and SG, and explains possible molecular mechanisms for poor grain filling in IG. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Root growth, soil water variation, and grain yield response of winter wheat to supplemental irrigation

Directory of Open Access Journals (Sweden)

Jianguo Man

2016-04-01

Full Text Available Water shortage threatens agricultural sustainability in the Huang-Huai-Hai Plain of China. Thus, we investigated the effect of supplemental irrigation (SI on the root growth, soil water variation, and grain yield of winter wheat in this region by measuring the moisture content in different soil layers. Prior to SI, the soil water content (SWC at given soil depths was monitored to calculate amount of irritation water that can rehydrate the soil to target SWC. The SWC before SI was monitored to depths of 20, 40, and 60 cm in treatments of W20, W40, and W60, respectively. Rainfed treatment with no irrigation as the control (W0. The mean root weight density (RWD, triphenyl tetrazolium chloride reduction activity (TTC reduction activity, soluble protein (SP concentrations as well as catalase (CAT, and superoxide dismutase (SOD activities in W40 and W60 treatments were significantly higher than those in W20. The RWD in 60–100 cm soil layers and the root activity, SP concentrations, CAT and SOD activities in 40–60 cm soil layers in W40 treatment were significantly higher than those in W20 and W60. W40 treatment is characterized by higher SWC in the upper soil layers but lower SWC in the 60–100-cm soil layers during grain filling. The soil water consumption (SWU in the 60–100 cm soil layers from anthesis after SI to maturity was the highest in W40. The grain yield, water use efficiency (WUE, and irrigation water productivity were the highest in W40, with corresponding mean values of 9169 kg ha−1, 20.8 kg ha−1 mm−1, and 35.5 kg ha−1 mm−1. The RWD, root activities, SP concentrations, CAT and SOD activities, and SWU were strongly positively correlated with grain yield and WUE. Therefore, the optimum soil layer for SI of winter wheat after jointing is 0–40 cm.

Densification and Grain Growth during Early-stage Sintering of Ce0.9Gd0.1O1.95-δ in Reducing Atmosphere

DEFF Research Database (Denmark)

He, Zeming; Yuan, Hao; Glasscock, Julie

2010-01-01

The present work investigates the processes of densification and grain growth of Ce0.9Gd0.1O1.95-δ (CGO10) during sintering in reducing atmosphere. Sintering variables were experimentally characterized and analyzed using defect chemistry and sintering constitutive laws. Based on the achieved...

The effects of surface finish and grain size on the strength of sintered silicon carbide

Science.gov (United States)

You, Y. H.; Kim, Y. W.; Lee, J. G.; Kim, C. H.

1985-01-01

The effects of surface treatment and microstructure, especially abnormal grain growth, on the strength of sintered SiC were studied. The surfaces of sintered SiC were treated with 400, 800 and 1200 grit diamond wheels. Grain growth was induced by increasing the sintering times at 2050 C. The beta to alpha transformation occurred during the sintering of beta-phase starting materials and was often accompanied by abnormal grain growth. The overall strength distributions were established using Weibull statistics. The strength of the sintered SiC is limited by extrinsic surface flaws in normal-sintered specimens. The finer the surface finish and grain size, the higher the strength. But the strength of abnormal sintering specimens is limited by the abnormally grown large tabular grains. The Weibull modulus increases with decreasing grain size and decreasing grit size for grinding.

Analysis of recrystallization and grain growth in ultra low carbon steels using EBSD

International Nuclear Information System (INIS)

Novillo, E.; Petite, M. M.; Bocos, J. L.; Gutierrez, I.

2004-01-01

This work is focused on the study of recrystallization texture and micro texture in a cold rolled ultra low carbon steel and its relationship with the global texture. Aspects like nucleation, evolution of the volume fraction and grain size were considered. An important grain selection associated with a significant size and number advantages of the recrystallized grains is observed. This grain selection gives rise to the development, at the latest stages of recrystallization, of a strong γ-fibre associated to good drawing properties. (Author) 24 refs

Mechanism for selective growth in electrical steel

Science.gov (United States)

Oh, Eun Jee; Heo, Nam Hoe; Kwon, Se Kyun; Koo, Yang Mo

2018-01-01

Through the competitive selective growth process between {100}, {110}, and {111} grains during final annealing which is governed by the primary grain size and the surface segregation concentration of sulfur, the sharp {110} annealing texture can be developed in a C-and Al-free Fe-3%Si-0.1%Mn electrical steel. Generally, the selective growth of the {110} grains occurs actively under the low surface segregation concentration of sulfur. In spite of the surface energy disadvantage, the selective growth of a {hkl} grain can however occur, if the {hkl} grain size is larger than the critical grain size linearly proportional to the strip thickness.

Experimental investigation of grain size effect on fatigue crack growth rate in turbine disc superalloy GH4169 under different temperatures

Energy Technology Data Exchange (ETDEWEB)

Hu, Dianyin [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China); Mao, Jianxing [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Song, Jun, E-mail: jun.song2@mcgill.ca [Mining and Materials Engineering, McGill University, Montreal, QC, Canada H3A 0C5 (Canada); Meng, Fanchao [Mining and Materials Engineering, McGill University, Montreal, QC, Canada H3A 0C5 (Canada); Shan, Xiaoming [China Aviation Powerplant Research Institute, Zhuzhou 412002 (China); Wang, Rongqiao, E-mail: wangrq@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191 (China); Beijing Key Laboratory of Aero-Engine Structure and Strength, Beijing 100191 (China)

2016-07-04

Systematic experiments for fatigue crack growth (FCG) rate on compact tension (CT) specimens have been conducted in nickel-based superalloy GH4169 at a broad range of temperatures with a frequency of 10 Hz and a stress ratio of 0.1. In order to investigate the crack closure behavior, FCG experiments at stress ratio of 0.5 were also performed by comparing with the results at stress ration of 0.1. CT specimens were cut from three typical locations of an actual forged turbine disc to investigate the effect of grain size on the FCG behaviors. The grain size distribution, precipitates and fracture surface characteristics at different locations of the turbine disc were examined through optical microscope, transmission electron microscope (TEM) and scanning electronic microscope (SEM) analyses. Digital image correlation (DIC), optical interferometry and oxide film measurements were carried out to investigate the presence and inducement of the crack closure. Then a modified FCG model, with a distribution factor that evaluates the scattering in the FCG rate, was formulated to describe the dependence of FCG rate on grain size. Finally, the possible microscopic mechanisms to explain the grain size effect on the FCG behaviors based on crack deflection and blockage, and the crack closure inducements involving plasticity and oxide were discussed in this study.

Grain formation in cool stellar envelopes

International Nuclear Information System (INIS)

Deguchi, S.

1980-01-01

The nucleation and growth of dust grains in the stellar envelope are investigated for the case of oxygen-rich stars, where the mass loss occurs as a result of the radiation pressure on the dust grains. The number density of grains, the final grain sizes, and the final amount of metals remaining in gaseous states are calculated based on the grain-nucleation theory proposed by Yamamoto and Hasegawa and Draine and Salpeter. It is shown that, even if we base our calculations on the Lothe-Pound nucleation rate equation instead of the classical, homogeneous nucleation rate equation, the proposed theory gives a number density of grains quite similar to that based on the classical rate equation. The approximate solution of the flow, in this paper, brings physical insight to the problem of how the formation of grains couples the flow passing the sonic point. The metals in the outer envelope remain in gaseous state by the amount of 1--10% of the initial content for the mass-loss rate of 10 -5 M/sub sun/ yr -1 and by less than 1% for the massloss are less than 3 x 10 -6 M/sub sun/ yr -1 . Species of metals condensed onto the grains are also discussed

INFRARED SPECTROSCOPIC SURVEY OF THE QUIESCENT MEDIUM OF NEARBY CLOUDS. I. ICE FORMATION AND GRAIN GROWTH IN LUPUS

Energy Technology Data Exchange (ETDEWEB)

Boogert, A. C. A. [IPAC, NASA Herschel Science Center, Mail Code 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Chiar, J. E. [SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Knez, C.; Mundy, L. G. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Öberg, K. I. [Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Pendleton, Y. J. [Solar System Exploration Research Virtual Institute, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Tielens, A. G. G. M.; Van Dishoeck, E. F., E-mail: aboogert@ipac.caltech.edu [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

2013-11-01

Infrared photometry and spectroscopy (1-25 μm) of background stars reddened by the Lupus molecular cloud complex are used to determine the properties of grains and the composition of ices before they are incorporated into circumstellar envelopes and disks. H{sub 2}O ices form at extinctions of A{sub K} = 0.25 ± 0.07 mag (A{sub V} = 2.1 ± 0.6). Such a low ice formation threshold is consistent with the absence of nearby hot stars. Overall, the Lupus clouds are in an early chemical phase. The abundance of H{sub 2}O ice (2.3 ± 0.1 × 10{sup –5} relative to N{sub H}) is typical for quiescent regions, but lower by a factor of three to four compared to dense envelopes of young stellar objects. The low solid CH{sub 3}OH abundance (<3%-8% relative to H{sub 2}O) indicates a low gas phase H/CO ratio, which is consistent with the observed incomplete CO freeze out. Furthermore it is found that the grains in Lupus experienced growth by coagulation. The mid-infrared (>5 μm) continuum extinction relative to A{sub K} increases as a function of A{sub K}. Most Lupus lines of sight are well fitted with empirically derived extinction curves corresponding to R{sub V} ∼ 3.5 (A{sub K} = 0.71) and R{sub V} ∼ 5.0 (A{sub K} = 1.47). For lines of sight with A{sub K} > 1.0 mag, the τ{sub 9.7}/A{sub K} ratio is a factor of two lower compared to the diffuse medium. Below 1.0 mag, values scatter between the dense and diffuse medium ratios. The absence of a gradual transition between diffuse and dense medium-type dust indicates that local conditions matter in the process that sets the τ{sub 9.7}/A{sub K} ratio. This process is likely related to grain growth by coagulation, as traced by the A{sub 7.4}/A{sub K} continuum extinction ratio, but not to ice mantle formation. Conversely, grains acquire ice mantles before the process of coagulation starts.

Grain Structure Control of Additively Manufactured Metallic Materials

Directory of Open Access Journals (Sweden)

Fuyao Yan

2017-11-01

Full Text Available Grain structure control is challenging for metal additive manufacturing (AM. Grain structure optimization requires the control of grain morphology with grain size refinement, which can improve the mechanical properties of additive manufactured components. This work summarizes methods to promote fine equiaxed grains in both the additive manufacturing process and subsequent heat treatment. Influences of temperature gradient, solidification velocity and alloy composition on grain morphology are discussed. Equiaxed solidification is greatly promoted by introducing a high density of heterogeneous nucleation sites via powder rate control in the direct energy deposition (DED technique or powder surface treatment for powder-bed techniques. Grain growth/coarsening during post-processing heat treatment can be restricted by presence of nano-scale oxide particles formed in-situ during AM. Grain refinement of martensitic steels can also be achieved by cyclic austenitizing in post-processing heat treatment. Evidently, new alloy powder design is another sustainable method enhancing the capability of AM for high-performance components with desirable microstructures.

Simulation of growing grains under orientation relation - dependent quadruple point dragging

International Nuclear Information System (INIS)

Ito, K

2015-01-01

The growth behaviour of a specified grain embedded in matrix grains, for which the migration mobility of the quadruple points depended on the relation between the orientations of the growing and shrinking grains, was studied using a modified Potts MC-type threedimensional simulation. Large embedded grains continued to grow without being overcome by coarsening matrix grains, whereas small embedded grains disappeared, under the influence of the relative mobilities of the quadruple points, the composition of the matrix grain texture and the width of the grain size distribution of the matrix grains. These results indicate that orientation relation-dependent quadruple point dragging can affect the recrystallization texture during the grain coarsening stage. (paper)

Effects of Nano-Zinc oxide and Seed Inoculation by Plant Growth Promoting Rhizobacteria (PGPR on Yield, Yield Components and Grain Filling Period of Soybean (Glycine max L.

Directory of Open Access Journals (Sweden)

R. Seyed Sharifi

2016-02-01

promoting rhizobacteria application on yield, yield components and grain filling period of soybean. Materials and Methods In order to study the effects of Nano-Zinc oxide and seed inoculation with Brady rhizobium and plant growth promoting rhizobacteria on yield and some agronomic characteristics of soybean, a factorial experiment based on randomized complete block design with three replications was conducted in 2013 at the research farm of the Islamic Azad University, Ardabil Branch. Factors were included foliar application of Nano-Zinc oxide at four levels (Zero as control, 0.3, 0.6 and 0.9 g l-1 and seed inoculation with Brady rhizobium and plant growth promoting rhizobacteria at five levels (without inoculation as control, seed inoculation with Brady rhizobium japanicum, seed inoculation with Brady rhizobium japanicum+Azosprillum lipoferum strain OF, seed inoculation with Brady rhizobium japanicum+Psedomonas putida, seed inoculation with Brady rhizobium japanicum+ Azosprillum lipoferum strain OF+ Psedomonas putida. Results and Discussion The results of growth indices showed that the maximum total dry matter (530 g m-2, crop growth rate (9.48 g.m-2.day-1 and relative growth rate (0.1 g.g-1.day-1 were obtained at foliar application of 0.9 g l-1 Nano-Zinc oxide×seed inoculation with rhizobium+Azosprillum+ Psedomonas and the least of these indices were obtained without of foliar application Nano-Zinc oxide × seed inoculation. The results showed that plant height, the number of nodules per plant, the number of pod per plant, grain yield and grain 100 weight were significantly affected by Nano-Zinc oxide, seed inoculation and interaction of Nano-Zinc oxide×seed inoculation. Maximum of plant height, grain 100 weight, the number of nodules per plant and grain yield were obtained at foliar application of 0.9 g l-1 of Nano-Zinc oxide×seed inoculation with rhizobium and PGPR. Dry weight of nodules per plant, the number of pod per plant and the number of grains per plant

Coarse-graining and hybrid methods for efficient simulation of stochastic multi-scale models of tumour growth

International Nuclear Information System (INIS)

Cruz, Roberto de la; Guerrero, Pilar; Calvo, Juan; Alarcón, Tomás

2017-01-01

The development of hybrid methodologies is of current interest in both multi-scale modelling and stochastic reaction–diffusion systems regarding their applications to biology. We formulate a hybrid method for stochastic multi-scale models of cells populations that extends the remit of existing hybrid methods for reaction–diffusion systems. Such method is developed for a stochastic multi-scale model of tumour growth, i.e. population-dynamical models which account for the effects of intrinsic noise affecting both the number of cells and the intracellular dynamics. In order to formulate this method, we develop a coarse-grained approximation for both the full stochastic model and its mean-field limit. Such approximation involves averaging out the age-structure (which accounts for the multi-scale nature of the model) by assuming that the age distribution of the population settles onto equilibrium very fast. We then couple the coarse-grained mean-field model to the full stochastic multi-scale model. By doing so, within the mean-field region, we are neglecting noise in both cell numbers (population) and their birth rates (structure). This implies that, in addition to the issues that arise in stochastic-reaction diffusion systems, we need to account for the age-structure of the population when attempting to couple both descriptions. We exploit our coarse-graining model so that, within the mean-field region, the age-distribution is in equilibrium and we know its explicit form. This allows us to couple both domains consistently, as upon transference of cells from the mean-field to the stochastic region, we sample the equilibrium age distribution. Furthermore, our method allows us to investigate the effects of intracellular noise, i.e. fluctuations of the birth rate, on collective properties such as travelling wave velocity. We show that the combination of population and birth-rate noise gives rise to large fluctuations of the birth rate in the region at the leading edge

High Heat Load Properties of Ultra Fine Grain Tungsten

International Nuclear Information System (INIS)

Zhou, Z.; Du, J.; Ge, C.; Linke, J.; Pintsuk, G.; Song, S.X.

2007-01-01

Full text of publication follows: Tungsten is increasingly considered as a promising candidate armour materials facing the plasma in tokamaks for medium to high heat flux components (EAST, ASDEX, ITER). Fabrication tungsten with ultra fine grain size is considered as an effective way to ameliorate some disadvantages of tungsten, such as its brittleness at room temperature. But the research data on the performance of ultra fine grain tungsten is still very limit. In this work, high heat load properties of pure ultra-fine grain tungsten have been studied. The ultra fine grain tungsten samples with average grain size of 0.2 μm, 1 μm and 3 μm were fabricated by resistance sintering under ultra high pressure. The annealing experiments for the investigation of the material resistance against grain growth have been done by annealing samples in a vacuum furnace at different temperature holding for 2 hours respectively. It is found that recrystallization and grain growth occur at heating temperature of 1250 deg. c. The finer the initial grain sizes of tungsten, the smaller its grain growth grain. The effects of transient high thermal loads (off normal events like disruptions) on tungsten surface morphology have been performed in electron beam test facility JUDITH. The thermal loads tests have been carried out with 4 ms pulses at different power density of 0.22, 0.33, 0.44, 0.55 and 0.88 GW/m 2 respectively. Horizontal cracks formed for all tungsten samples at 0.44 GW/m 2 . Particle erosions occurred for tungsten with 3 μm size at 0.33 GW/m 2 and for tungsten with 0.2 and 1 μm size at 0.55 GW/m 2 . The weight loss of tungsten with 0.2, 1 and 3 μm size are 2,0.1,0.6 mg respectively at 0.88 GW/m 2 . The effects of a large number of very short transient repetitive thermal loads (ELM-like) on tungsten surface morphology also have been performed by using a fundamental wave of a YAG laser. It is found that tungsten with 0.2 μm size has the best performance. (authors)

High Heat Load Properties of Ultra Fine Grain Tungsten

Energy Technology Data Exchange (ETDEWEB)

Zhou, Z.; Du, J.; Ge, C. [Lab. of Special Ceramic and P/M, University of Science and Technology, 100083 Beijing (China); Linke, J.; Pintsuk, G. [FZJ-Forschungszentrum Juelich GmbH, Association Euratom-FZJ, Institut fur Plasmaphysik, Postfach 1913, D-52425 Juelich (Germany); Song, S.X. [Research Center on Fusion Materials (RCFM), University of Science and Technology Beijing (USTB), 100083 Beijing (China)

2007-07-01

Full text of publication follows: Tungsten is increasingly considered as a promising candidate armour materials facing the plasma in tokamaks for medium to high heat flux components (EAST, ASDEX, ITER). Fabrication tungsten with ultra fine grain size is considered as an effective way to ameliorate some disadvantages of tungsten, such as its brittleness at room temperature. But the research data on the performance of ultra fine grain tungsten is still very limit. In this work, high heat load properties of pure ultra-fine grain tungsten have been studied. The ultra fine grain tungsten samples with average grain size of 0.2 {mu}m, 1 {mu}m and 3 {mu}m were fabricated by resistance sintering under ultra high pressure. The annealing experiments for the investigation of the material resistance against grain growth have been done by annealing samples in a vacuum furnace at different temperature holding for 2 hours respectively. It is found that recrystallization and grain growth occur at heating temperature of 1250 deg. c. The finer the initial grain sizes of tungsten, the smaller its grain growth grain. The effects of transient high thermal loads (off normal events like disruptions) on tungsten surface morphology have been performed in electron beam test facility JUDITH. The thermal loads tests have been carried out with 4 ms pulses at different power density of 0.22, 0.33, 0.44, 0.55 and 0.88 GW/m{sup 2} respectively. Horizontal cracks formed for all tungsten samples at 0.44 GW/m{sup 2}. Particle erosions occurred for tungsten with 3 {mu}m size at 0.33 GW/m{sup 2} and for tungsten with 0.2 and 1 {mu}m size at 0.55 GW/m{sup 2}. The weight loss of tungsten with 0.2, 1 and 3 {mu}m size are 2,0.1,0.6 mg respectively at 0.88 GW/m{sup 2}. The effects of a large number of very short transient repetitive thermal loads (ELM-like) on tungsten surface morphology also have been performed by using a fundamental wave of a YAG laser. It is found that tungsten with 0.2 {mu}m size has

Effect of V-Nd co-doping on phase transformation and grain growth process of TiO2

Science.gov (United States)

Khatun, Nasima; Amin, Ruhul; Anita, Sen, Somaditya

2018-05-01

The pure and V-Nd co-doped TiO2 samples are prepared by the modified sol-gel process. The phase formation is confirmed by XRD spectrum. Phase transformation is delayed in V-Nd co-doped TiO2 (TVN) samples compared to pure TiO2. The particle size is comparatively small in TVN samples at both the temperature 450 °C and 900 °C. Hence the effect of Nd doping is dominated over V doping in both phase transformation and grain growth process of TiO2.

Transitional grain-size-sensitive flow of milky quartz aggregates

Science.gov (United States)

Fukuda, J. I.; Holyoke, C. W., III; Kronenberg, A. K.

2014-12-01

Fine-grained (~15 μm) milky quartz aggregates exhibit reversible flow strengths in triaxial compression experiments conducted at T = 800-900oC, Pc = 1.5 GPa when strain rates are sequentially decreased (typically from 10-3.5 to 10-4.5 and 10-5.5 s-1), and then returned to the original rate (10-3.5 s-1), while samples that experience grain growth at 1000oC (to 35 μm) over the same sequence of strain rates exhibit an irreversible increase in strength. Polycrystalline quartz aggregates have been synthesized from natural milky quartz powders (ground to 5 μm) by HIP methods at T = 1000oC, Pc = 1.5 GPa and t = 24 hours, resulting in dense, fine-grained aggregates of uniform water content of ~4000 ppm (H/106Si), as indicated by a broad OH absorption band at 3400 cm-1. In experiments performed at 800o and 900oC, grain sizes of the samples are essentially constant over the duration of each experiment, though grain shapes change significantly, and undulatory extinction and deformation lamellae indicate that much of the sample shortening (to 50%) is accomplished, over the four strain-rate steps, by dislocation creep. Differential stresses measured at T = 800oC decrease from 160 to 30 MPa as strain rate is reduced from 10-4.6 to 10-5.5 s-1, and a stress of 140 MPa is measured when strain rate is returned to 10-4.5 s-1. Samples deformed at 1000o and 1100oC experience normal grain growth, with grain boundary energy-driven grain-coarsening textures superposed by undulatory extinction and deformation lamellae. Differential stresses measured at 1000oC and strain rates of 10-3.6, 10-4.6, and 10-5.5 s-1 are 185, 80, and 80 MPa, respectively, while an increased flow stress of 260 MPa is measured (following ~28 hours of prior high temperature deformation and grain growth) when strain rate is returned to 10-3.6 s-1. While all samples exhibit lattice preferred orientations, the stress exponent n inferred for the fine-grained 800oC sample is 1.5 and the stress exponent of the coarse-grained

Formation of intra-island grain boundaries in pentacene monolayers.

Science.gov (United States)

Zhang, Jian; Wu, Yu; Duhm, Steffen; Rabe, Jürgen P; Rudolf, Petra; Koch, Norbert

2011-12-21

To assess the formation of intra-island grain boundaries during the early stages of pentacene film growth, we studied sub-monolayers of pentacene on pristine silicon oxide and silicon oxide with high pinning centre density (induced by UV/O(3) treatment). We investigated the influence of the kinetic energy of the impinging molecules on the sub-monolayer growth by comparing organic molecular beam deposition (OMBD) and supersonic molecular beam deposition (SuMBD). For pentacene films fabricated by OMBD, higher pentacene island-density and higher polycrystalline island density were observed on UV/O(3)-treated silicon oxide as compared to pristine silicon oxide. Pentacene films deposited by SuMBD exhibited about one order of magnitude lower island- and polycrystalline island densities compared to OMBD, on both types of substrates. Our results suggest that polycrystalline growth of single islands on amorphous silicon oxide is facilitated by structural/chemical surface pinning centres, which act as nucleation centres for multiple grain formation in a single island. Furthermore, the overall lower intra-island grain boundary density in pentacene films fabricated by SuMBD reduces the number of charge carrier trapping sites specific to grain boundaries and should thus help achieving higher charge carrier mobilities, which are advantageous for their use in organic thin-film transistors.

Observation of changing crystal orientations during grain coarsening

International Nuclear Information System (INIS)

Sharma, Hemant; Huizenga, Richard M.; Bytchkov, Aleksei; Sietsma, Jilt; Offerman, S. Erik

2012-01-01

Understanding the underlying mechanisms of grain coarsening is important in controlling the properties of metals, which strongly depend on the microstructure that forms during the production process or during use at high temperature. Grain coarsening of austenite at 1273 K in a binary Fe–2 wt.% Mn alloy was studied using synchrotron radiation. Evolution of the volume, average crystallographic orientation and mosaicity of more than 2000 individual austenite grains was tracked during annealing. It was found that an approximately linear relationship exists between grain size and mosaicity, which means that orientation gradients are present in the grains. The orientation gradients remain constant during coarsening and consequently the character of grain boundaries changes during coarsening, affecting the coarsening rate. Furthermore, changes in the average orientation of grains during coarsening were observed. The changes could be understood by taking the observed orientation gradients and anisotropic movement of grain boundaries into account. Five basic modes of grain coarsening were deduced from the measurements, which include: anisotropic (I) and isotropic (II) growth (or shrinkage); movement of grain boundaries resulting in no change in volume but a change in shape (III); movement of grain boundaries resulting in no change in volume and mosaicity, but a change in crystallographic orientation (IV); no movement of grain boundaries (V).

Modification of the grain structure of austenitic welds for improved ultrasonic inspectability

International Nuclear Information System (INIS)

Wagner, S.; Dugan, S.; Stubenrauch, S.; Jacobs, O.

2012-01-01

Austenitic stainless steel welds, which are widely used for example in nuclear power plants and chemical installations, present major challenges for ultrasonic inspection due to the grain structure of the weld. Large grains in combination with the elastic anisotropy of the material lead to increased scattering and affect sound wave propagation in the weld. This results in a reduced signal-to-noise ratio, and complicates the interpretation of signals and the localization of defects. The aim of this project is to influence grain growth in the weld during the welding process to produce smaller grains, in order to improve sound propagation through the weld, thus improving inspectability. Metallographic sections of the first test welds have shown that a modification of the grain structure can be achieved by influencing the grain growth with magnetic fields. For further optimization, test blocks for ultrasonic testing were manufactured to study sound propagation through the weld and detectability of test flaws.

Effect of grain size upon the fatigue-crack propagation behavior of alloy 718 under hold-time cycling at elevated temperature

Energy Technology Data Exchange (ETDEWEB)

James, L A

1986-01-01

Fatigue-crack propagation tests were conducted in air at 538/sup 0/C on several specimens of Alloy 718 representing several different producers, melt practices and product forms. This variety resulted in a range of grain sizes from ASTM Size 5 to 11.5. Tests at low cyclic frequency employing a tensile hold-time revealed a relationship between crack growth rates and grain size: higher growth rates were associated with fine-grain material and lower rates with larger-grain material. The lowest crack growth rates were associated with a necklace microstructure, whereby large grains are associated with necklaces of very small grains.

Oxygen Permeability and Grain-Boundary Diffusion Applied to Alumina Scales

Science.gov (United States)

Smialek, James L.; Jacobson, Nathan S.; Gleeson, Brian; Hovis, David B.; Heuer, Arthur H.

2013-01-01

High-temperature oxygen permeability measurements had determined grain-boundary diffusivities (deltaD(sub gb)) in bulk polycrystalline alumina (Wada, Matsudaira, and Kitaoka). They predict that oxygen deltaD(sub gb,O) varies with oxygen pressure as P(O2)(sup -1/6) at low pressure whereas aluminum deltaD(sub gb),Al varies with P(O2)(sup +3/16) at high pressure. These relations were used to evaluate alumina scale growth in terms of diffusivity and grain size. A modified Wagner treatment for dominant inward oxygen growth produces the concise solution: ?(sub i) = k(sub p,i)×G(sub i) = 12 deltaD(sub gb,O,int), where ?(sub i) is a constant and k(sub p,i) and G(sub i) refer to instantaneous values of the scale parabolic growth constant and grain size, respectively. A commercial FeCrAl(Zr) alloy was oxidized at 1100 to 1400 degC to determine k(sub p,i), interfacial grain size, ?, and thus deltaD(sub gb,O,int). The deltaD(sub gb,O,int) values predicted from oxidation at (375 kJ/mole) were about 20 times less than those obtained above (at 298 kJ/mole), but closer than extrapolations from high-temperature bulk measurements. The experimental oxidation results agree with similar FeCrAl(X) studies, especially where both k(sub p,i) and G(sub i) were characterized. This complete approach accounts for temperature-sensitive oxidation effects of grain enlargement, equilibrium interface pressure variation, and grain-boundary diffusivity.

Effect of hot band grain size on development of textures and magnetic properties in 2.0% Si non-oriented electrical steel sheet

Energy Technology Data Exchange (ETDEWEB)

Lee, K.M. [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Huh, M.Y., E-mail: myhuh@korea.ac.kr [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Lee, H.J.; Park, J.T.; Kim, J.S. [Electrical Steel Sheet Research Group, Technical Research Laboratories, POSCO, Goedong-dong, Pohang (Korea, Republic of); Shin, E.J. [Korea Atomic Energy Research Institute, Neutron Science Division, Daejeon 305-353 (Korea, Republic of); Engler, O. [Hydro Aluminium Rolled Products GmbH, Research and Development Bonn, P.O. Box 2468, D-53014 Bonn (Germany)

2015-12-15

The effect of hot band grain size on the development of crystallographic texture and magnetic properties in non-oriented electrical steel sheet was studied. After cold rolling the samples with different initial grain sizes displayed different microstructures and micro-textures but nearly identical macro-textures. The homogeneous recrystallized microstructure and micro-texture in the sample having small grains caused normal continuous grain growth. The quite irregular microstructure and micro-texture in the recrystallized sample with large initial grain size provided a preferential growth of grains in 〈001〉//ND and 〈113〉//ND which were beneficial for developing superior magnetic properties. - Highlights: • We produced hot bands of electrical steel with different grain size but same texture. • Hot band grain size strongly affected cold rolling and subsequent annealing textures. • Homogeneous recrystallized microstructure caused normal continuous grain growth. • Irregular recrystallized microstructure led to selective growth of <001>//ND grains. • Hot band with large grains was beneficial for superior magnetic properties.

Discrete stochastic charging of aggregate grains

Science.gov (United States)

Matthews, Lorin S.; Shotorban, Babak; Hyde, Truell W.

2018-05-01

Dust particles immersed in a plasma environment become charged through the collection of electrons and ions at random times, causing the dust charge to fluctuate about an equilibrium value. Small grains (with radii less than 1 μm) or grains in a tenuous plasma environment are sensitive to single additions of electrons or ions. Here we present a numerical model that allows examination of discrete stochastic charge fluctuations on the surface of aggregate grains and determines the effect of these fluctuations on the dynamics of grain aggregation. We show that the mean and standard deviation of charge on aggregate grains follow the same trends as those predicted for spheres having an equivalent radius, though aggregates exhibit larger variations from the predicted values. In some plasma environments, these charge fluctuations occur on timescales which are relevant for dynamics of aggregate growth. Coupled dynamics and charging models show that charge fluctuations tend to produce aggregates which are much more linear or filamentary than aggregates formed in an environment where the charge is stationary.

An Overview of Grain Growth Theories for Pure Single Phase Systems,

Science.gov (United States)

1986-10-01

the fundamental causes for these distributions. This Blanc and Mocellin (1979) and Carnal and Mocellin (1981j set out to do. 7.1 Monte-Carlo Simulations...termed event B) (in 2-D) of 3-sided grains. (2) Neighbour-switching (termed event C). Blanc and Mocellin (1979) dealt with 2-D sections through...Kurtz and Carpay (1980a). 7.2 Analytical Method to Obtain fn Carnal and Mocellin (1981) obtained the distribution of grain coordination numbers in

The effects of particle size distribution and induced unpinning during grain growth

International Nuclear Information System (INIS)

Thompson, G.S.; Rickman, J.M.; Harmer, M.P.; Holm, E.A.

1996-01-01

The effect of a second-phase particle size distribution on grain boundary pinning was studied using a Monte Carlo simulation technique. Simulations were run using a constant number density of both whisker and rhombohedral particles, and the effect of size distribution was studied by varying the standard deviation of the distribution around a constant mean particle size. The results of present simulations indicate that, in accordance with the stereological assumption of the topological pinning model, changes in distribution width had no effect on the pinned grain size. The effect of induced unpinning of particles on microstructure was also studied. In contrast to predictions of the topological pinning model, a power law dependence of pinned grain size on particle size was observed at T=0.0. Based on this, a systematic deviation to the stereological predictions of the topological pinning model is observed. The results of simulations at higher temperatures indicate an increasing power law dependence of pinned grain size on particle size, with the slopes of the power law dependencies fitting an Arrhenius relation. The effect of induced unpinning of particles was also studied in order to obtain a correlation between particle/boundary concentration and equilibrium grain size. The results of simulations containing a constant number density of monosized rhombohedral particles suggest a strong power law correlation between the two parameters. copyright 1996 Materials Research Society

Drought Stress Effect during Different Growth Stages on Yield, Osmolites and Photosynthetic Pigments Accumulation of Grain Sorghum Genotypes (Sorghum bicolor L.

Directory of Open Access Journals (Sweden)

A Azari Nasrabad

2017-12-01

Full Text Available Introduction Osmotic adjustment in plants can be achieved by the accumulation of compatible solution or metabolites. These compounds are known as compatible metabolites that accumulate naturally in tolerant plants due to non-interference in the normal metabolic response of plants to adapt or supplement. Proline, soluble sugars and other metabolites accumulation that are involved in osmotic adjustment have been reported for various plants. Different studies show that water absorption in sorghum plant, is due to osmotic adjustment and appropriate and fairly extensive root system. Moreover, there are some differences from genotype to genotype regarding the osmolites accumulation under drought stress conditions. Thus, the aim of this study was to investigate the effects of drought in the vegetative and reproductive growth stages on yield, its components and biochemical traits in grain sorghum genotypes. Materials and Methods In order to evaluate the effect of water stress on grain yield and its components and some biochemical traits in grain sorghum genotypes (Sorghum bicolor L., a field experiment as a split plot design was carried out with 3 replications in 2014 at the research farm of the southern Khorasan Agriculture and natural resources research and education center. Water stress treatments including normal irrigation (control, irrigation cut off in vegetative growth stage (emergence of terminal leaf as rolled and irrigation cut off in generative growth stage (50% of plants in start of flowering as the main plot and 10 genotypes of sorghum including KGS29, MGS2, Sepideh, KGFS27, MGS5, KGFS5, KGFS17, KGFS13 and KGFS30 were considered as sub plots. Each plot consists of 4 rows with a length of 6 m and row spacing of 60 cm, between plants on row was 10 cm. In addition, between each plot and the adjacent plot a row was considered to side effect reduction. To determine the yield components of each plot, half a meter in length was harvested and the

DEVELOPMENT OF GRAIN MARKET IN UKRAINE

Directory of Open Access Journals (Sweden)

Aleksandr Maslak

2015-11-01

Full Text Available The subject of the research is a set of theoretical, methodological and practical fundamentals of organizational and economic functioning are integrated agricultural formations in the grain market of Ukraine. The methodological basis of research is the complex analysis of economic processes in the grain market in Ukraine and the world. During research we used such methods as method of systematization and comparison, statistic, economic, balance, constructive, target-oriented, and the methods of induction and deduction, analogy and comparison. Main aim of this article is the analysis of the situation on the grain market in Ukraine, defining the role of integrated agricultural formations in this market, improving the organizational-economic mechanism of its functioning, identifies ways of improving the competitiveness of Ukraine among world exporters of grain. Using results of the studies we examined trends grain market in Ukraine; influence of businesses in grain production; analysis of constraints to improve production efficiency of grain; defined domestic (internal needs of grain in Ukraine; assessed the status and expediency transformation infrastructure of the grain market of Ukraine; defined priority directions of development of the grain market in Ukraine. As a result of the preparation of articles, it is obtained the following conclusions: Ukraine is the world's largest producers and exporters of grain, the production of integrated agricultural units to a third of the total grain; technical condition of farm does not meet the needs of production; the domestic market is unable to provide the existing demand for grain production, contributing to export growth; Ukraine has a number of problems due to increased grain production, namely the shortage of storage capacity for the storage of grain, limited performance transshipment of grain in port elevators and imperfection and depreciation of transport systems; solving the existing problems is

Creep crack extension by grain-boundary cavitation

International Nuclear Information System (INIS)

Bassani, J.L.

1981-01-01

Recent work by Riedel and coworkers has led to various descriptions of stationary and moving crack tip fields under creep conditions. For stationary and growing cracks, several flow mechanisms (e.g., elastic, time-independent plastic, primary creep, and secondary creep) can dictate the analytical form of the crack tip field. In this paper, relationship between overall loading and crack velocities are modelled based upon grain-boundary cavity growth and coalescence within the zone of concentrated strain in the crack tip field. Coupled diffusion and creep growth of the cavities is considered. Overall crack extension is taken to be intermittent on a size scale equivalent to the size of a grain. Numerical results are presented for a center-cracked panel of 304 stainless steel. (author)

Texture development due to preferential grain growth of Ho--Ba--Cu--O in 1.6-T magnetic field

International Nuclear Information System (INIS)

Holloway, A.; McCallum, R.W.; Arrasmith, S.R.

1993-01-01

It has been experimentally observed that the application of even a relatively weak magnetic field of 1.6-T during sintering of HoBa 2 Cu 3 O 7-δ (hereafter HoBCO) results in a significant degree of grain alignment. The orientation of grains is found to be controlled by the direction and magnitude of a magnetic field. The degree of alignment was monitored by x-ray diffraction measurements on the flat surface of the samples and by metallography. It has been observed that the degree of alignment grows as the magnitude of the field increases between 0 and 1.6 T for a fixed temperature and processing time. The degree of alignment also increases when the processing temperature changes from 930 degree C to 965 degree C for a fixed field and time. It has also been observed that for both a fixed field and processing temperature, the alignment grows when the processing time increases between 16 and 72 hours. Metallography measurements on the flat and cross-sectional parts of the samples showed that the texture propagates into the bulk of the samples. In the presence of a sufficient amount of the liquid phase, the enhancement of the grain growth in the direction favorable to the magnetic field produces rather large single-crystals (0.3 to 0.5 mm linear size) within the sample

Twinned feathery grains and related morphologies in aluminum alloys

Energy Technology Data Exchange (ETDEWEB)

Henry, S. [Compagnie de Produits Chimiques et Electrometallurgiques Pechiney, Centre de Recherches de Voreppe, 38 (France); Lab. de Metallurgie Physique, Ecole Polytechnique Federale de Lausanne (Switzerland); Rappaz, M. [Lab. de Metallurgie Physique, Ecole Polytechnique Federale de Lausanne (Switzerland)

2000-07-01

Al-Cu, Al-Mg and Al-Si alloys without grain refiner addition have been directionally solidified under well-controlled thermal and convection conditions. For relatively high solidification rates, several changes in the dendrite growth morphology were observed. One of the most common structure that may appear under such conditions is called ''feathery grains'' : it was demonstrated recently that this lamellar structure is constituted of left angle 110 right angle dendrites whose trunks are cut through by {l_brace}111{r_brace} twin planes. These grains undergo a selection mechanism which is similar to that occurring for regular left angle 100 right angle dendritic grains. The transition between left angle 100 right angle and left angle 110 right angle dendrite forms is progressive and morphologies that develop arms in both type of crystallographic directions can be observed. Moreover, in the case of a 5182 Al-Mg alloy, regular left angle 110 right angle dendrites, without twins, could also be obtained. This dendritic growth along left angle 110 right angle crystallographic directions is supposed to be due to a change in the anisotropy of certain properties of the alloy, such as the solid/liquid interfacial energy and/or the atom attachment kinetics. The possibility of growth along other directions than the usual left angle 100 right angle was further demonstrated by the observation of dendrites developing in an Al-Cu-Mg solidified in a Bridgman device. In this case, left angle 112 right angle trunks form and progressively change their growth direction, thus showing curved shapes. (orig.)

Deformation inhomogeneity in large-grained AA5754 sheets

International Nuclear Information System (INIS)

Zhu Guozhen; Hu Xiaohua; Kang Jidong; Mishra, Raja K.; Wilkinson, David S.

2011-01-01

Research highlights: → Microstructure and strain relationship at individual grain level was studied. → 'Hot spots' nucleate early and most keep growing throughout deformation stages. → 'Hot spots' are correlated with 'soft' grains and soft-evolution grains. → Grains with high Schmid factors tend to be 'soft' grains. → Grains with the direction close to tensile axis tend to become softer. - Abstract: Models for deformation and strain localization in polycrystals that incorporate microstructural features including particles are computationally intensive due to the large variation in scale in going from particles to grains to a specimen. As a result such models are generally 2-D in nature. This is an issue for experimental validation. We have therefore studied deformation heterogeneities and strain localization behavior of coarse-grained alloys with only two grains across the sample thickness, therefore mimicking 2-D behavior. Aluminum alloy sheets (AA5754) have been investigated by a number of surface techniques, including digital image correlation, slip trace analysis and electron backscattered diffraction, at the individual grain level. Local strain concentration zones appear from the very beginning of deformation, which then maintain sustained growth and lead, in one of these regions, to localization and final fracture. These 'hot spots' occur in areas with locally soft grains (i.e. grains with or close to the tensile direction) and soft-evolution orientations (i.e. grains with close to the tensile direction). These grains can be correlated with Taylor and/or Schmid factors.

Modeling the effect of neighboring grains on twin growth in HCP polycrystals

Science.gov (United States)

Kumar, M. Arul; Beyerlein, I. J.; Lebensohn, R. A.; Tomé, C. N.

2017-09-01

In this paper, we study the dependence of neighboring grain orientation on the local stress state around a deformation twin in a hexagonal close packed (HCP) crystal and its effects on the resistance against twin thickening. We use a recently developed, full-field elasto-visco-plastic formulation based on fast Fourier transforms that account for the twinning shear transformation imposed by the twin lamella. The study is applied to Mg, Zr and Ti, since these HCP metals tend to deform by activation of different types of slip modes. The analysis shows that the local stress along the twin boundary are strongly controlled by the relative orientation of the easiest deformation modes in the neighboring grain with respect to the twin lamella in the parent grain. A geometric expression that captures this parent-neighbor relationship is proposed and incorporated into a larger scale, mean-field visco-plastic self-consistent model to simulate the role of neighboring grain orientation on twin thickening. We demonstrate that the approach improves the prediction of twin area fraction distribution when compared with experimental observations.

New 3DXRD results on recrystallization and grain growth

DEFF Research Database (Denmark)

Juul Jensen, Dorte; West, Stine; Poulsen, Stefan Othmar

2012-01-01

New in-situ 3DXRD results obtained since the last Rex&GG conference are presented and discussed. This includes: Documentation of the formation of nuclei with new orientations, determination of apparent activation energies for individual bulk grains during recrystallization and evolution in the 3D...

Generalized coarse-grained Becker-Doering equations

International Nuclear Information System (INIS)

Bolton, Colin D; Wattis, Jonathan A D

2003-01-01

We present and apply a generalized coarse-graining method of reducing the Becker-Doering model; originally formulated to describe the stepwise aggregation and fragmentation of clusters during nucleation. Previous formulations of the coarse-graining procedure have allowed a temporal rescaling of the coarse-grained reaction rates; this is generalized to allow the rescaling to depend on cluster size. The form of this factor is derived for general reaction rates and general mesh function so that the steady-state solution is preserved; in the case of an even mesh function the kinetics can also be accurately reproduced. With a size-dependent mesh function the equilibrium solution and the form of convergence to this state are matched for a specific example. Finally we consider reaction rates relevant to the classical nucleation theory of spherical cluster growth, and numerically compare solutions of the full system to the generalized coarse-grained system in both constant monomer and constant mass formulations, demonstrating the accuracy of the method

Concentration contours in lattics and grain boundary diffusion in a polycrystalline solid

International Nuclear Information System (INIS)

Kim, Yong Soo; Jae, Won Mok; El Saied, Usama; Olander, Donald R.

1995-01-01

Grain boundary diffusion plays significant role in the fission gas release, which is one of the crucial processes dominating nuclear fuel performance. Gaseous fission products such as Xe and Kr generated inside fuel pellet have to diffuse in the lattice and in the grain boundary before they reach open space in the fuel rod. In the mean time, the grains in the fuel pellet grow and shrink according to grain growth kinetics, especially at elevated temperature at which nuclear reactors are operating. Thus the boundary movement ascribed to the grain growth greatly influences the fission gas release rate by lengthening or shortening the lattice diffusion distance, which is the rate limiting step. Sweeping fission gases by the moving boundary contributes to the increment of the fission gas release as well. Lattice and grain boundary diffusion processes in the fission gas release can be studied by 'tracer diffusion' technique, by which grain boundary diffusivity can be estimated and used directly for low burn up fission gas release analysis. However, even for tracer diffusion analysis, taking both the intragranular grain growth and the diffusion processes simultaneously into consideration is not easy. Only a few models accounting for the both processes are available and mostly handle them numerically. Numerical solutions are limited in the practical use. Here in this paper, an approximate analytical solution of the lattice and stationary grain boundary diffusion in a polycrystalline solid is developed for the tracer diffusion techniques. This short closed form solution is compared to available exact and numerical solutions and turns out to be acceptably accurate. It can be applied to the theoretical modeling and the experimental analysis, especially PIE (post irradiation examination), of low burn up fission gas release

Evolution of grain structure in nickel oxide scales

International Nuclear Information System (INIS)

Atkinson, H.V.

1987-01-01

In systems such as the oxidation of nickel, in which grain-boundary diffusion in the oxide can control the rate of oxidation, understanding of the factors governing the grain structure is of importance. High-purity mechanically polished polycrystalline nickel was oxidized at 700 0 C, 800 0 C, and 1000 0 C for times up to 20 hr in 1 atm O 2 . The scale microstructures were examined by parallel and transverse cross section transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Texture coefficients were found by x-ray diffraction (XRD). Each grain in the transverse section grain boundary networks was systematically analyzed for width parallel to the Ni-NiO interface and perpendicular length, for boundary radius of curvature and for number of sides. The variation of these parameters with depth in the scale was examined. In particular, grains were increasingly columnar (i.e., with ratio of grain length to width > 1) at higher temperatures and longer times. Columnar grain boundaries tended to be fairly static; the columnar grain width was less than the rate controlling grain size predicted from the oxidation rate. The mean boundary curvature per grain provided a guide to the tendency for grain growth, except in the region of the Ni-NiO interface, where the boundaries were thought to be pinned

A Cosserat crystal plasticity and phase field theory for grain boundary migration

Science.gov (United States)

Ask, Anna; Forest, Samuel; Appolaire, Benoit; Ammar, Kais; Salman, Oguz Umut

2018-06-01

The microstructure evolution due to thermomechanical treatment of metals can largely be described by viscoplastic deformation, nucleation and grain growth. These processes take place over different length and time scales which present significant challenges when formulating simulation models. In particular, no overall unified field framework exists to model concurrent viscoplastic deformation and recrystallization and grain growth in metal polycrystals. In this work a thermodynamically consistent diffuse interface framework incorporating crystal viscoplasticity and grain boundary migration is elaborated. The Kobayashi-Warren-Carter (KWC) phase field model is extended to incorporate the full mechanical coupling with material and lattice rotations and evolution of dislocation densities. The Cosserat crystal plasticity theory is shown to be the appropriate framework to formulate the coupling between phase field and mechanics with proper distinction between bulk and grain boundary behaviour.

Interactions of impurities with a moving grain boundary

Energy Technology Data Exchange (ETDEWEB)

Bauer, C L [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA)

1975-01-01

Most theories developed to explain interaction of impurities with a moving grain boundary involve a uniform excess impurity concentration distributed along a planar grain boundary. As boundary velocity increases, the excess impurities exert a net drag force on the boundary until a level is reached whereat the drag force no longer can balance the driving force and breakaway of the boundary from these impurities occurs. In this investigation, assumptions of a uniform lateral impurity profile and a planar grain boundary shape are relaxed by allowing both forward and lateral diffusion of impurities in the vicinity of a grain boundary. It is found that the two usual regions (drag of impurities by, and breakaway of a planar grain boundary) are separated by an extensive region wherein a uniform lateral impurity profile and a planar grain boundary shape are unstable. It is suspected that, in this unstable region, grain boundaries assume a spectrum of more complex morphologies and that elucidation of these morphologies can provide the first definitive description of the breakaway process and insight to more complex phenomena such as solid-solution strengthening, grain growth and secondary recrystallization.

Grain boundary corrosion of copper canister material

International Nuclear Information System (INIS)

Fennell, P.A.H.; Graham, A.J.; Smart, N.R.; Sofield, C.J.

2001-03-01

The proposed design for a final repository for spent fuel and other long-lived residues in Sweden is based on the multi-barrier principle. The waste will be encapsulated in sealed cylindrical canisters, which will then be placed in granite bedrock and surrounded by compacted bentonite clay. The canister design is based on a thick cast inner container fitted inside a corrosion-resistant copper canister. During fabrication of the outer copper canisters there will be some unavoidable grain growth in the welded areas. As grains grow they will tend to concentrate impurities within the copper at the new grain boundaries. The work described in this report was undertaken to determine whether there is any possibility of enhanced corrosion at grain boundaries within the copper canister. The potential for grain boundary corrosion was investigated by exposing copper specimens, which had undergone different heat treatments and hence had different grain sizes, to aerated artificial bentonite-equilibrated groundwater with two concentrations of chloride, for increasing periods of time. The degree of grain boundary corrosion was determined by atomic force microscopy (AFM) and optical microscopy. AFM showed no increase in grain boundary 'ditching' for low chloride groundwater. In high chloride groundwater the surface was covered uniformly with a fine-grained oxide. No increases in oxide thickness were observed. No significant grain boundary attack was observed using optical microscopy either. The work suggests that in aerated artificial groundwaters containing chloride ions, grain boundary corrosion of copper is unlikely to adversely affect SKB's copper canisters

Influence of Alloy and Solidification Parameters on Grain Refinement in Aluminum Weld Metal due to Inoculation

Energy Technology Data Exchange (ETDEWEB)

Schempp, Philipp [BAM, Germany; Tang, Z. [BIAS, Germany; Cross, Carl E. [Los Alamos National Laboratory; Seefeld, T. [BIAS, Germany; Pittner, A. [BAM, Germany; Rethmeier, M. [BAM, Germany

2012-06-28

The goals are: (1) Establish how much Ti/B grain refiner is need to completely refine aluminum weld metal for different alloys and different welding conditions; (2) Characterize how alloy composition and solidification parameters affect weld metal grain refinement; and (3) Apply relevant theory to understand observed behavior. Conclusions are: (1) additions of Ti/B grain refiner to weld metal in Alloys 1050, 5083, and 6082 resulted in significant grain refinement; (2) grain refinement was more effective in GTAW than LBW, resulting in finer grains at lower Ti content - reason is limited time available for equiaxed grain growth in LBW (inability to occlude columnar grain growth); (3) welding travel speed did not markedly affect grain size within GTAW and LBW clusters; and (4) application of Hunt CET analysis showed experimental G to be on the order of the critical G{sub CET}; G{sub CET} was consistently higher for GTAW than for LBW.

Consequences of diverse use of nitrogen sources on grain yield ...

African Journals Online (AJOL)

A two year field experiment was conducted to check the consequences of diverse use of nitrogen sources on grain yield, grain quality and growth attributes of hybrid maize (Zea mays L.) at the Agronomic Research Area, University of Agriculture, Faisalabad during Autumn 2008 and 2009. Experiments were laid out in a ...

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

Directory of Open Access Journals (Sweden)

Florian Steinbach

2017-09-01

Full Text Available The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modeling and analyzed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD have been used together with c-axis orientations using an optical technique (Fabric Analyser. Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighboring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modeling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be

The relevance of grain dissection for grain size reduction in polar ice: insights from numerical models and ice core microstructure analysis

Science.gov (United States)

Steinbach, Florian; Kuiper, Ernst-Jan N.; Eichler, Jan; Bons, Paul D.; Drury, Martyn R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

2017-09-01

The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to

Factors affecting the grain growth of austenite in low alloy steel

International Nuclear Information System (INIS)

Parker, J.D.; Storer, S.M.

1995-01-01

The performance of steels is linked to the metallurgical transformations which occur during manufacture. Clearly then the optimization of a fabrication procedure must be based on fundamental relationships linking specific thermal treatments with transformation behaviour. Optimized manufacture of thick-section, multipass welds is therefore particularly complex since the thermal cycles associated with fusion welding result in the formation of heterogeneous microstructures. Moreover, these transformations will take place under rapid heating and cooling conditions so that standard data based on equilibrium behaviour may not be directly relevant. The present study is part of an integrated research programme aimed at establishing the basic microstructural relationships required to optimize the manufacture and performance of weldments. Work to date demonstrates that utilization of a computer controlled Gleeble simulation system allows a wider range of heating and cooling rates to be applied than is possible with traditional heat treatment techniques. Additional advantages of this system include precise control of time at peak temperature and uniform temperatures within a defined work zone. Results presented for a CrMoV creep resistant low alloy steel indicate that grain growth behaviour in the range 955-1390 C can be related to the time at peak temperature. The effect of this transformation behaviour on weldment behaviour is discussed. (orig.)

Effect of nutrition, vitamin, grains, and temperature on the mycelium growth and antioxidant capacity of Cordyceps militaris (strains AG-1 and PSJ-1

Directory of Open Access Journals (Sweden)

Hung-Ngoc Dang

2018-04-01

Full Text Available Effects of subculture conditions on the mycelium growth and antioxidant capacity assessment of Cordyceps militaris trains AG-1 and PSJ-1 were carried out in laboratory during the autumn-winter season of 2015. Different temperature regimes and nutrition, vitamins levels, grain in substrate were evaluated for optimization on mycelium growth. The results showed that two strains AG-1 and PSJ-1 can grow the maximum mycelium radial at the temperature of 24 °C. The mycelium growth was improved by carbon sources such as glucose, dextrose, fructose, and maltose at 30 g/L concentration. Whereas glucose achieved the highest value of mycelium colony diameter in strains AG-1 and PSJ-1. Vitamins B1 concentrations at 0.03 g/L also gave the great values in mycelium colony diameter of both strains AG-1 and PSJ-1. The studies depicted that a substrate mixed with various grains sources (brown rice, white rice, and wheat, black glutinous rice Vietnam, and corn cultured at 24 °C, for 12 days supported maximum mycelia growth of the two strains AG-1 and PSJ-1 of C. militaris. The effect of liquid culture medium (MYPS and PD with mycelium on the anti-oxidation capacity was assessed. The results showed that the increasing of DPPH radical scavenging capacity with the extract concentration exist a proportional relation and Fe2+-chelating capacity as well. The cultured Cordyceps mycelium of two strains AG-1 and PSJ-1had the equally strong antioxidant capacity. Keywords: Cordyceps militaris, Mycelium growth, Nutritional condition, Temperature, Vitamins, Anti-oxidation activity

Ensuring sustainable grain legume-cereal cropping systems

DEFF Research Database (Denmark)

Bedoussac, Laurent; Journet, E-P; Hauggaard-Nielsen, Henrik

2017-01-01

health makes them a key rotation crop in the sustainable intensification and diversification of smallholder farming. This makes grain legumes a key food security crop. However, yields in developing countries are low as a result of such factors as the need for improved varieties of seed, poor seed......Grain legumes are widely cultivated, particularly for their dry seeds (known as pulses). Grain legumes are an important crop for a number of reasons. They are a rich source of protein and fibre, minerals and vitamins. In addition, their rapid growth and ability to fix nitrogen and improve soil...... distribution, the impact of pests and diseases, as well as vulnerability to poor soils, drought and other effects of climate change. This chapter summarises data from over 50 field experiments undertaken since 2001 on cereal-grain legume intercropping in 13 sites in southern and western France as well...

Grain boundary engineering of highly deformable ceramics

International Nuclear Information System (INIS)

Mecartney, M.L.

2000-01-01

Highly deformable ceramics can be created with the addition of intergranular silicate phases. These amorphous intergranular phases can assist in superplastic deformation by relieving stress concentrations and minimizing grain growth if the appropriate intergranular compositions are selected. Examples from 3Y-TZP and 8Y-CSZ ceramics are discussed. The grain boundary chemistry is analyzed by high resolution analytical TEM is found to have a strong influence on the cohesion of the grains both at high temperature and at room temperature. Intergranular phases with a high ionic character and containing large ions with a relatively weak bond strength appear to cause premature failure. In contrast, intergranular phases with a high degree of covalent character and similar or smaller ions than the ceramic and a high ionic bond strength are the best for grain boundary adhesion and prevention of both cavitation at high temperatures and intergranular fracture at room temperature

Development of Perennial Grain Sorghum

Directory of Open Access Journals (Sweden)

Stan Cox

2018-01-01

Full Text Available Perennial germplasm derived from crosses between Sorghum bicolor and either S. halepense or S. propinquum is being developed with the goal of preventing and reversing soil degradation in the world’s grain sorghum-growing regions. Perennial grain sorghum plants produce subterranean stems known as rhizomes that sprout to form the next season’s crop. In Kansas, breeding perennial sorghum involves crossing S. bicolor cultivars or breeding lines to S. halepense or perennial S. bicolorn × S. halepense breeding lines, selecting perennial plants from F2 or subsequent populations, crossing those plants with S. bicolor, and repeating the cycle. A retrospective field trial in Kansas showed that selection and backcrossing during 2002–2009 had improved grain yields and seed weights of breeding lines. Second-season grain yields of sorghum lines regrowing from rhizomes were similar to yields in the first season. Further selection cycles have been completed since 2009. Many rhizomatous lines that cannot survive winters in Kansas are perennial at subtropical or tropical locations in North America and Africa. Grain yield in Kansas was not correlated with rhizomatousness in either Kansas or Uganda. Genomic regions affecting rhizome growth and development have been mapped, providing new breeding tools. The S. halepense gene pool may harbor many alleles useful for improving sorghum for a broad range of traits in addition to perenniality.

Consequences of diverse use of nitrogen sources on grain yield ...

African Journals Online (AJOL)

Muhammad Waseem

2012-08-28

Aug 28, 2012 ... sources on grain yield, grain quality and growth attributes of hybrid maize (Zea mays L.) at the. Agronomic Research Area, University ...... rate were found in 2009. Evans et al. (2003) also noted similar interactive effects of hybrid and N sources in maize. In year 2008, contrasts comparison (Table 4) between ...

Rotation-limited growth of three-dimensional body-centered-cubic crystals.

Science.gov (United States)

Tarp, Jens M; Mathiesen, Joachim

2015-07-01

According to classical grain growth laws, grain growth is driven by the minimization of surface energy and will continue until a single grain prevails. These laws do not take into account the lattice anisotropy and the details of the microscopic rearrangement of mass between grains. Here we consider coarsening of body-centered-cubic polycrystalline materials in three dimensions using the phase field crystal model. We observe, as a function of the quenching depth, a crossover between a state where grain rotation halts and the growth stagnates and a state where grains coarsen rapidly by coalescence through rotation and alignment of the lattices of neighboring grains. We show that the grain rotation per volume change of a grain follows a power law with an exponent of -1.25. The scaling exponent is consistent with theoretical considerations based on the conservation of dislocations.

Defects in fine-grained and porous materials characterized by positron annihilation

International Nuclear Information System (INIS)

Staab, T.E.M.; Krause-Rehberg, R.; Kieback, B.

2003-01-01

We investigate the annihilation parameters (lifetimes and intensities) for positrons becoming trapped at grain boundaries and at inner surfaces (pores), examining fine-grained nickel powder compacts (effective powder particle size 1 - 10 μm with grains in or even below the micron size). Furthermore, we can monitor grain growth and sintering (volume shrinkage) during successive heat treatment of powder compacts. To reach this aim, we correlate the annihilation parameters with results of a Monte-Carlo simulation and analytical solutions of the positron diffusion. We find that it is possible to determine an effective average powder particle size as well as grain sizes by positron lifetime spectroscopy. (author)

Growth behavior of fatigue cracks in ultrafine grained Cu smooth specimens with a small hole

Directory of Open Access Journals (Sweden)

Masahiro Goto

2015-10-01

Full Text Available In order to study the growth mechanism of fatigue cracks in ultrafine grained copper, stresscontrolled fatigue tests of round-bar specimens with a small blind hole as a crack starter were conducted. The hole was drilled on the surface where an intersection between the shear plane of the final ECAP processing and the specimen surface makes an angle of 45° or 90° with respect to the loading axis. At a low stress (  a = 90 MPa, the direction of crack paths was nearly perpendicular to the loading direction regardless of the location of the hole. Profile of crack face was examined, showing the aspect ratio (b/a of b/a = 0.82. At a high stress (  a = 240 MPa, although the growth directions inclined 45° and 90° to the loading-axis were observed depending on the location of the drilling hole, crack faces in these cracks were extended along one set of maximum shear stress planes, corresponding to the final ECAP shear plane. The value of aspect ratios was b/a = 0.38 and 1.10 for the cracks with 45° and 90° inclined path directions, respectively. The role of deformation mode at the crack tip areas on crack growth behavior were discussed in terms of the mixed-mode stress intensity factor. The crack path formation at high stress amplitudes was affected by the in-plane shear-mode deformation at the crack tip.

Enhancement effects of dietary wheat distiller's dried grains with solubles on growth, immunology, and resistance to Edwardsiella ictaluri challenge of channel catfish, Ictalurus punctatus

Science.gov (United States)

This study evaluated the effects of the inclusion of wheat distiller’s dried grains with solubles (WDDGS) at levels of 0 (control), 10, 20, 30 and 40% without (diets 2-5) and with (diets 6-9) lysine supplementation, as substitutes of soybean meal and corn meal mixture on growth, body composition, he...

Isotropic Growth of Graphene toward Smoothing Stitching.

Science.gov (United States)

Zeng, Mengqi; Tan, Lifang; Wang, Lingxiang; Mendes, Rafael G; Qin, Zhihui; Huang, Yaxin; Zhang, Tao; Fang, Liwen; Zhang, Yanfeng; Yue, Shuanglin; Rümmeli, Mark H; Peng, Lianmao; Liu, Zhongfan; Chen, Shengli; Fu, Lei

2016-07-26

The quality of graphene grown via chemical vapor deposition still has very great disparity with its theoretical property due to the inevitable formation of grain boundaries. The design of single-crystal substrate with an anisotropic twofold symmetry for the unidirectional alignment of graphene seeds would be a promising way for eliminating the grain boundaries at the wafer scale. However, such a delicate process will be easily terminated by the obstruction of defects or impurities. Here we investigated the isotropic growth behavior of graphene single crystals via melting the growth substrate to obtain an amorphous isotropic surface, which will not offer any specific grain orientation induction or preponderant growth rate toward a certain direction in the graphene growth process. The as-obtained graphene grains are isotropically round with mixed edges that exhibit high activity. The orientation of adjacent grains can be easily self-adjusted to smoothly match each other over a liquid catalyst with facile atom delocalization due to the low rotation steric hindrance of the isotropic grains, thus achieving the smoothing stitching of the adjacent graphene. Therefore, the adverse effects of grain boundaries will be eliminated and the excellent transport performance of graphene will be more guaranteed. What is more, such an isotropic growth mode can be extended to other types of layered nanomaterials such as hexagonal boron nitride and transition metal chalcogenides for obtaining large-size intrinsic film with low defect.

Microstructural investigation of grain stability in cryomilled inconel 625

International Nuclear Information System (INIS)

Chung, K.H.; Lee, J.; Rodriguez, R.; Lavernia, E.J.; Shin, D.H.

2002-01-01

The grain growth behavior of nanocrystalline Inconel 625 powders prepared by cryomilling (mechanical milling under a liquid nitrogen environment) was investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The average grain size of powders after 8 hours cryomilling was 22 nm. Along with this fine structure, ultrafine NiO and Cr 2 O 3 oxide particles were distributed in the cryomilled material with average size of 3 nm. It was found that the grain size remain under 250 nm after 4 hours heat treatment at 800 C, which correspond to T/T m ∝0.65. The cryomilled Inconel 625 showed improved grain stability compared to that of conventional Inconel 625 and cryomilled pure-Ni, due to the particle pinning of grain boundary by the oxide particles in addition to solute drag. (orig.)

Verification of “Channel-Probability Model” of Grain Yield Estimation

Directory of Open Access Journals (Sweden)

ZHENG Hong-yan

2016-07-01

Full Text Available The "channel-probability model" of grain yield estimation was verified and discussed systematically by using the grain production data from 1949 to 2014 in 16 typical counties, and 6 typical districts, and 31 provinces of China. The results showed as follows:(1Due to the geographical spatial scale was large enough, different climate zones and different meteorological conditions could compensated, and grain yield estimation error was small in the scale of nation. Therefore, it was not necessary to modify the grain yield estimation error by mirco-trend and the climate year types in the scale of nation. However, the grain yield estimation in the scale of province was located at the same of a climate zone,the scale was small, so the impact of the meteorological conditions on grain yield was less complementary than the scale of nation. While the spatial scale of districts and counties was smaller, accordingly the compensation of the impact of the meteorological conditions on grain yield was least. Therefore, it was necessary to use mrico-trend amendment and the climate year types amendment to modify the grain yield estimation in districts and counties.(2Mirco-trend modification had two formulas, generally, when the error of grain yield estimation was less than 10%, it could be modified by Y×(1-K; while the error of grain yield estimation was more than 10%, it could be modified by Y/(1+K.(3Generally, the grain estimation had 5 grades, and some had 7 grades because of large error fluctuation. The parameters modified of super-high yield year and super-low yield year must be depended on the real-time crop growth and the meteorological condition. (4By plenty of demonstration analysis, it was proved that the theory and method of "channel-probability model" was scientific and practical. In order to improve the accuracy of grain yield estimation, the parameters could be modified with micro-trend amendment and the climate year types amendment. If the

Formation of dust grains with impurities in red giant winds

Science.gov (United States)

Dominik, Carsten

1994-01-01

Among the several proposed carriers of diffuse interstellar bands (DIB's) are impurities in small dust grains, especially in iron oxide grains (Huffman 1977) and silicate grains (Huffman 1970). Most promising are single ion impurities since they can reproduce the observed band widths (Whittet 1992). These oxygen-rich grains are believed to originate mostly in the mass flows from red giants and in supernovae ejecta (e.g. Gehrz 1989). A question of considerable impact for the origin of DIB's is therefore, whether these grains are produced as mainly clean crystals or as some dirty materials. A formalism has been developed that allows tracking of the heterogeneous growth of a dust grain and its internal structure during the dust formation process. This formalism has been applied to the dust formation in the outflow from a red giant star.

Stress corrosion cracking of stainless steel under deaerated high-temperature water. Influence of grain boundary carbide precipitation

International Nuclear Information System (INIS)

Yamada, Takuyo; Terachi, Takumi; Arioka, Koji

2006-01-01

In order to evaluate the influence of grain boundary carbide on IGSCC susceptibility, crack growth rate tests were performed under deaerated and 0.3 ppm hydrogenated pure water environments at 320degC using half-inch compact tension specimens. To investigate various grain boundary carbide conditions, three kinds of SUS316 - non-sensitized, sensitized at 650degC for 1 hour or 48 hours - were prepared. To examine the influence of grain boundary carbide, the grain boundary conditions of those materials were investigated by transmission electron microscopy and energy dispersive x-ray spectroscopy. As a result, (1) IGSCC crack growth was observed on non sensitized and cold worked SUS316 under deaerated and 0.3 ppm hydrogenated water environments at 320degC; (2) Any trace of IGSCC crack growth was not observed on sensitized at 650degC for 48 hours and cold worked SUS316 under the same water environments; (3) The SUS316 sensitized at 650degC for 48 hours showed extensive M 23 C 6 precipitation as well as Cr depletion at grain boundaries. These differences in IGSCC crack growth rate indicate that grain boundary carbide has the beneficial effect of improving IGSCC susceptibility, at least under deaerated and 0.3 ppm hydrogenated water environments, despite chromium depletion at the grain boundary. (author)

Microstructure of warm rolling and pearlitic transformation of ultrafine-grained GCr15 steel

International Nuclear Information System (INIS)

Sun, Jun-Jie; Lian, Fu-Liang; Liu, Hong-Ji; Jiang, Tao; Guo, Sheng-Wu; Du, Lin-Xiu; Liu, Yong-Ning

2014-01-01

Pearlitic transformation mechanisms have been investigated in ultra-fine grained GCr15 steel. The ultrafine-grained steel, whose grain size was less than 1 μm, was prepared by thermo-mechanical treatment at 873 K and then annealing at 923 K for 2 h. Pearlitic transformation was conducted by reheating the ultra-fine grained samples at 1073 K and 1123 K for different periods of time and then cooling in air. Scanning electron microscope observation shows that normal lamellar pearlite, instead of granular cementite and ferrite, cannot be formed when the grain size is approximately less than 4(± 0.6) μm, which yields a critical grain size for normal lamellar pearlitic transformations in this chromium alloyed steel. The result confirms that grain size has a great influence on pearlitic transformation by increasing the diffusion rate of carbon atoms in the ultra-fine grained steel, and the addition of chromium element doesn't change this pearlitic phase transformation rule. Meanwhile, the grain growth rate is reduced by chromium alloying, which is beneficial to form fine grains during austenitizing, thus it facilitating pearlitic transformation by divorced eutectoid transformation. Moreover, chromium element can form a relatively high gradient in the frontier of the undissolved carbide, which promotes carbide formation in the frontier of the undissolved carbide, i.e., chromium promotes divorced eutectoid transformation. - Highlights: • Ultrafine-grained GCr15 steel was obtained by warm rolling and annealing technology. • Reduction of grain size makes pearlite morphology from lamellar to granular. • Adding Cr does not change normal pearlitic phase transformation rule in UFG steel. • Cr carbide resists grain growth and facilitates pearlitic transformation by DET

Increasing abscisic acid levels by immunomodulation in barley grains induces precocious maturation without changing grain composition.

Science.gov (United States)

Staroske, Nicole; Conrad, Udo; Kumlehn, Jochen; Hensel, Götz; Radchuk, Ruslana; Erban, Alexander; Kopka, Joachim; Weschke, Winfriede; Weber, Hans

2016-04-01

Abscisic acid (ABA) accumulates in seeds during the transition to the seed filling phase. ABA triggers seed maturation, storage activity, and stress signalling and tolerance. Immunomodulation was used to alter the ABA status in barley grains, with the resulting transgenic caryopses responding to the anti-ABA antibody gene expression with increased accumulation of ABA. Calculation of free versus antibody-bound ABA reveals large excess of free ABA, increasing signficantly in caryopses from 10 days after fertilization. Metabolite and transcript profiling in anti-ABA grains expose triggered and enhanced ABA-functions such as transcriptional up-regulation of sucrose-to-starch metabolism, storage protein synthesis and ABA-related signal transduction. Thus, enhanced ABA during transition phases induces precocious maturation but negatively interferes with growth and development. Anti-ABA grains display broad constitutive gene induction related to biotic and abiotic stresses. Most of these genes are ABA- and/or stress-inducible, including alcohol and aldehyde dehydrogenases, peroxidases, chaperones, glutathione-S-transferase, drought- and salt-inducible proteins. Conclusively, ABA immunomodulation results in precocious ABA accumulation that generates an integrated response of stress and maturation. Repression of ABA signalling, occurring in anti-ABA grains, potentially antagonizes effects caused by overshooting production. Finally, mature grain weight and composition are unchanged in anti-ABA plants, although germination is somewhat delayed. This indicates that anti-ABA caryopses induce specific mechanisms to desensitize ABA signalling efficiently, which finally yields mature grains with nearly unchanged dry weight and composition. Such compensation implicates the enormous physiological and metabolic flexibilities of barley grains to adjust effects of unnaturally high ABA amounts in order to ensure and maintain proper grain development. © The Author 2016. Published by

Relative effect(s) of texture and grain size on magnetic properties in a low silicon non-grain oriented electrical steel

International Nuclear Information System (INIS)

PremKumar, R.; Samajdar, I.; Viswanathan, N.N.; Singal, V.; Seshadri, V.

2003-01-01

Hot rolled low Si (silicon) non-grain oriented electrical steel was cold rolled to different reductions. Cold rolled material was subsequently recrystallized, 650 deg. C and 2 h, and then temper rolled (to 7% reduction) for the final grain growth annealing and decarburization treatment at 850 deg. C for 2-24 h. The development of texture, grain size and magnetic properties were characterized at different stages of processing. Effect of texture on magnetic properties (watt loss and permeability) was observed to be best represented by the ratio of volume fractions of (1 1 1) /(0 0 1) fibers, as estimated by convoluting X-ray ODFs (orientation distribution functions) with respective model functions. Such a ratio was termed as generalized texture factor (tf) for the non-grain oriented electrical steel. An effort was made to delink effects of grain size and texture, as represented by respective tf, on watt loss and permeability by careful analysis of experimental data. In general, low tf and/or high grain size were responsible for low watt loss and high permeability. However, individual effect of grain size or tf on magnetic properties was less significant at low tf or large grain size, respectively. An attempt was made to fit regression equations, namely--linear, exponential and power, relating magnetic properties with tf and grain size, limiting the fitting parameters to 3. Least standard deviations, between experimental and predicted values, were obtained by power regression equations for both magnetic properties

Grain growth across protoplanetary discs: 10 μm silicate feature versus millimetre slope

NARCIS (Netherlands)

Lommen, D.J.P.; van Dishoeck, E.F.; Wright, C.M.; Min, M.

2010-01-01

Context. Young stars are formed with dusty discs around them. The dust grains in the disc are originally of the same size as interstellar dust, i.e., of the order of 0.1 μm. Models predict that these grains will grow in size through coagulation. Observations of the silicate features around 10 and 20

Combining x-ray diffraction contrast tomography and mesoscale grain growth simulations in strontium titanate: An integrated approach for the investigation of microstructure evolution

DEFF Research Database (Denmark)

Syha, Melanie; Baürer, Michael; Rheinheimer, Wolfgang

2013-01-01

Motivated by the recently reported a growth anomaly in strontium titatate bulk samples1, the microstructure of bulk strontium titanate has been investigated by an integrated approach comprising conventional metallography, three dimensional X-ray diffraction contrast tomography (DCT)2, and the obs......Motivated by the recently reported a growth anomaly in strontium titatate bulk samples1, the microstructure of bulk strontium titanate has been investigated by an integrated approach comprising conventional metallography, three dimensional X-ray diffraction contrast tomography (DCT)2......, and the observation of pore shapes in combination with mesoscale grain growth simulations. The microstructural evolution in strontium titanate has been characterized alternating ex-situ annealing and high energy X-ray DCT measurements, resulting in three dimensional microstructure reconstructions which...

Determination of grain boundary mobility during recrystallization by statistical evaluation of electron backscatter diffraction measurements

International Nuclear Information System (INIS)

Basu, I.; Chen, M.; Loeck, M.; Al-Samman, T.; Molodov, D.A.

2016-01-01

One of the key aspects influencing microstructural design pathways in metallic systems is grain boundary motion. The present work introduces a method by means of which direct measurement of grain boundary mobility vs. misorientation dependence is made possible. The technique utilizes datasets acquired by means of serial electron backscatter diffraction (EBSD) measurements. The experimental EBSD measurements are collectively analyzed, whereby datasets were used to obtain grain boundary mobility and grain aspect ratio with respect to grain boundary misorientation. The proposed method is further validated using cellular automata (CA) simulations. Single crystal aluminium was cold rolled and scratched in order to nucleate random orientations. Subsequent annealing at 300 °C resulted in grains growing, in the direction normal to the scratch, into a single deformed orientation. Growth selection was observed, wherein the boundaries with misorientations close to Σ7 CSL orientation relationship (38° 〈111〉) migrated considerably faster. The obtained boundary mobility distribution exhibited a non-monotonic behavior with a maximum corresponding to misorientation of 38° ± 2° about 〈111〉 axes ± 4°, which was 10–100 times higher than the mobility values of random high angle boundaries. Correlation with the grain aspect ratio values indicated a strong growth anisotropy displayed by the fast growing grains. The observations have been discussed in terms of the influence of grain boundary character on grain boundary motion during recrystallization. - Highlights: • Statistical microstructure method to measure grain boundary mobility during recrystallization • Method implementation independent of material or crystal structure • Mobility of the Σ7 boundaries in 5N Al was calculated as 4.7 × 10"–"8 m"4/J ⋅ s. • Pronounced growth selection in the recrystallizing nuclei in Al • Boundary mobility values during recrystallization 2–3 orders of magnitude

Effect of Primary Recrystallized Microstructure and Nitriding on Secondary Recrystallization in Grain Oriented Silicon Steel by Low Temperature Slab Reheating

Directory of Open Access Journals (Sweden)

LIU Gong-tao

2018-01-01

Full Text Available Different primary recrystallized grain sizes were obtained by controlling decarburization process in grain oriented silicon steel produced by low temperature slab reheating technique. The effect of primary grain size on secondary recrystallization and magnetic properties was studied. The appropriate nitrogen content after nitriding was explored in case of very large primary grain size, and the effect of {411}〈148〉 primary recrystallized texture on the abnormal growth behavior was discussed. The results show that an increase in average primary grain size from 10μm to 15μm leads to an increase of secondary recrystallization temperature and a sharper Goss texture with higher magnetic permeability, in the condition of a very large average primary grain size of 28μm, the suitable amount of nitrogen increases to about 6×10-4. The {411}〈148〉 oriented grains in primary recrystallized microstructure can easily grow into larger sizes due to their size advantage, and thus hinder the abnormal growth of secondary grains, moreover, the hindering effect is more pronounced in the abnormal growth of Brass-oriented grains due to their misorientation with low migration rate other than Goss grains.

Texturing of sodium bismuth titanate-barium titanate ceramics by templated grain growth

Science.gov (United States)

Yilmaz, Huseyin

2002-01-01

Sodium bismuth titanate modified with barium titanate, (Na1/2Bi 1/2)TiO3-BaTiO3 (NBT-BT), is a candidate lead-free piezoelectric material which has been shown to have comparatively high piezoelectric response. In this work, textured (Na1/2Bi1/2)TiO 3-BaTiO3 (5.5mol% BaTiO3) ceramics with pc (where pc denotes the pseudocubic perovskite cell) orientation were fabricated by Templated Grain Growth (TGG) or Reactive Templated Grain Growth (RTGG) using anisotropically shaped template particles. In the case of TGG, molten salt synthesized SrTiO3 platelets were tape cast with a (Na1/2Bi1/2)TiO3-5.5mol%BaTiO3 powder and sintered at 1200°C for up to 12 hours. For the RTGG approach, Bi4Ti3O12 (BiT) platelets were tape cast with a Na2CO3, Bi2O3, TiO 2, and BaCO3 powder mixture and reactively sintered. The TGG approach using SrTiO3 templates gave stronger texture along [001] compared to the RTGG approach using BiT templates. The textured ceramics were characterized by X-ray and electron backscatter diffraction for the quality of texture. The texture function was quantified by the Lotgering factor, rocking curve, pole figures, inverse pole figures, and orientation imaging microscopy. Electrical and electromechanical property characterization of randomly oriented and pc textured (Na1/2Bi1/2)TiO 3-5.5 mol% BaTiO3 rhombohedral ceramics showed 0.26% strain at 70 kV/cm, d33 coefficients over 500 pC/N have been obtained for highly textured samples (f ˜ 90%). The piezoelectric coefficient from Berlincourt was d33 ˜ 200 pC/N. The materials show considerable hysteresis. The presence of hysteresis in the unipolar-electric field curve is probably linked to the ferroelastic phase transition seen in the (Na 1/2Bi1/2)TiO3 system on cooling from high temperature at ˜520°C. The macroscopic physical properties (remanent polarization, dielectric constant, and piezoelectric coefficient) of random and textured ([001] pc) rhombohedral perovskites were estimated by linear averaging of single

Surface chemistry on interstellar oxide grains

International Nuclear Information System (INIS)

Denison, P.; Williams, D.A.

1981-01-01

Detailed calculations are made to test the predictions of Duley, Millar and Williams (1978) concerning the chemical reactivity of interstellar oxide grains. A method is established for calculating interaction energies between atoms and the perfect crystal with or without surface vacancy sites. The possibility of reactions between incident atoms and absorbed atoms is investigated. It is concluded that H 2 formation can occur on the perfect crystal surfaces, and that for other diatomic molecules the important formation sites are the Fsub(s)- and V 2- sub(s)-centres. The outline by Duley, Millar and Williams (1979) of interstellar oxide grain growth and destruction is justified by these calculations. (author)

Development of helium porosity near-by grain boundaries in nickel-carbon alloys

International Nuclear Information System (INIS)

Reutov, I.V.; Reutov, V.F.

1995-01-01

The peculiarities of development of helium porosity near grain boundaries in nickel with 0.002-0.065 at.% carbon uniformly doped with helium up to 2·10 -2 at.% in the process of post-irradiation isothermal annealing at 800 deg C for 1-50 hours are studied. It is stated that at this annealing temperature intensive nucleation and growth of bubbles are observed in near-boundary region whose width grows both with increase of annealing time and carbon content. The TEM studies have shown that in near-boundary zone itself the process of bubble growth is non-uniform: bubble size increases and their density decreases as the distance from grain boundary is increased. The effect observed is discussed from the point of view of formation of two zones with different level of swelling in a grain (near-by boundary and matrix) and consequently, hydrostatic stress as well conditioning the flux of vacancies and helium-vacancy complexes from matrix to grain boundary. 8 refs., 5 figs

Burst Testing and Analysis of Superalloy Disks With a Dual Grain Microstructure

Science.gov (United States)

Gayda, John; Kantzos, Pete

2006-01-01

Elastic-plastic finite element analyses of room temperature burst tests on four superalloy disks were conducted and reported in this paper. Two alloys, Rene 104 (General Electric Aircraft Engines) and Alloy 10 (Honeywell Engines & Systems), were studied. For both alloys an advanced dual microstructure disk, fine grain bore and coarse grain rim, were analyzed and compared with conventional disks with uniform microstructures, coarse grain for Rene 104 and fine grain for Alloy 10. The analysis and experimental data were in good agreement up to burst. At burst, the analysis underestimated the speed and growth of the Rene 104 disks, but overestimated the speed and growth of the Alloy 10 disks. Fractography revealed that the Alloy 10 disks displayed significant surface microcracking and coalescence in comparison to Rene 104 disks. This phenomenon may help explain the differences between the Alloy 10 disks and the Rene 104 disks, as well as the observed deviations between analytical and experimental data at burst.

Coarse-grained molecular simulation of epidermal growth factor receptor protein tyrosine kinase multi-site self-phosphorylation.

Directory of Open Access Journals (Sweden)

John G Koland

2014-01-01

Full Text Available Upon the ligand-dependent dimerization of the epidermal growth factor receptor (EGFR, the intrinsic protein tyrosine kinase (PTK activity of one receptor monomer is activated, and the dimeric receptor undergoes self-phosphorylation at any of eight candidate phosphorylation sites (P-sites in either of the two C-terminal (CT domains. While the structures of the extracellular ligand binding and intracellular PTK domains are known, that of the ∼225-amino acid CT domain is not, presumably because it is disordered. Receptor phosphorylation on CT domain P-sites is critical in signaling because of the binding of specific signaling effector molecules to individual phosphorylated P-sites. To investigate how the combination of conventional substrate recognition and the unique topological factors involved in the CT domain self-phosphorylation reaction lead to selectivity in P-site phosphorylation, we performed coarse-grained molecular simulations of the P-site/catalytic site binding reactions that precede EGFR self-phosphorylation events. Our results indicate that self-phosphorylation of the dimeric EGFR, although generally believed to occur in trans, may well occur with a similar efficiency in cis, with the P-sites of both receptor monomers being phosphorylated to a similar extent. An exception was the case of the most kinase-proximal P-site-992, the catalytic site binding of which occurred exclusively in cis via an intramolecular reaction. We discovered that the in cis interaction of P-site-992 with the catalytic site was facilitated by a cleft between the N-terminal and C-terminal lobes of the PTK domain that allows the short CT domain sequence tethering P-site-992 to the PTK core to reach the catalytic site. Our work provides several new mechanistic insights into the EGFR self-phosphorylation reaction, and demonstrates the potential of coarse-grained molecular simulation approaches for investigating the complexities of self-phosphorylation in

Analysis of grain filling process to the varied meteorological conditions in winter wheat [Triticum aestivum] cultivars

International Nuclear Information System (INIS)

Inoue, K.; Nakazono, K.; Wakiyama, Y.

2005-01-01

This paper describes effects of varied meteorological conditions on the grain filling periods, stabilities of yield and quality of winter wheat cultivars with different maturity characteristics (cv. Ayahikari, Norin61, Bandowase, and Tsurupikari). In the field experiments, the meteorological treatments were made during the first heading time on 17 April 2001 and the middle heading time on 24 April 2000. Air temperature, global solar radiation and soil moisture were controlled using a rain shelter, cheesecloth and irrigation system. The growth speed and growth period of wheat grains varied among four winter wheat cultivars, depending on meteorological conditions. The growth speed increased within 1 8.4 deg C of mean air temperature over the 30 days after the anthesis. On the other hand, it was found that the growth speed of wheat grains and the maximum number of wheat grains (Ymax) decreased greatly with the 44.4% interception of global solar radiation. Logistic functions were fitted to the relationship between the relative thousand-kernel-weight (Y/Ymax) and the total integrated temperature (sigmaTa) after heading for all treatment conditions. The maximum weight of grains (Ymax) achieved at the harvest time varied somewhat clearly among four winter wheat cultivars and meteorological conditions. Multiple regression analysis showed that the grain yield (Ymax) of four wheat cultivars correlated positively with daily mean solar radiation. It was also found that the cultivar Ayahikari had a highly significant negative correlation between its grain weight and soil moisture. Namely, the grain weight of high soil moisture plot with pF=1.5 was lower by about 9% than that of a control plot with pF=3.5. On the other hand, the grain yield of cultivar Norin61 responded inversely to a wet environment, indicating that its grain weight was higher for high soil moisture and high wet-bulb temperature than for a dry environment. The grain yield of early varieties of Bandowase and

PROTOPLANETARY DISK STRUCTURE WITH GRAIN EVOLUTION: THE ANDES MODEL

International Nuclear Information System (INIS)

Akimkin, V.; Wiebe, D.; Pavlyuchenkov, Ya.; Zhukovska, S.; Semenov, D.; Henning, Th.; Vasyunin, A.; Birnstiel, T.

2013-01-01

We present a self-consistent model of a protoplanetary disk: 'ANDES' ('AccretioN disk with Dust Evolution and Sedimentation'). ANDES is based on a flexible and extendable modular structure that includes (1) a 1+1D frequency-dependent continuum radiative transfer module, (2) a module to calculate the chemical evolution using an extended gas-grain network with UV/X-ray-driven processes and surface reactions, (3) a module to calculate the gas thermal energy balance, and (4) a 1+1D module that simulates dust grain evolution. For the first time, grain evolution and time-dependent molecular chemistry are included in a protoplanetary disk model. We find that grain growth and sedimentation of large grains onto the disk midplane lead to a dust-depleted atmosphere. Consequently, dust and gas temperatures become higher in the inner disk (R ∼ 50 AU), in comparison with the disk model with pristine dust. The response of disk chemical structure to the dust growth and sedimentation is twofold. First, due to higher transparency a partly UV-shielded molecular layer is shifted closer to the dense midplane. Second, the presence of big grains in the disk midplane delays the freeze-out of volatile gas-phase species such as CO there, while in adjacent upper layers the depletion is still effective. Molecular concentrations and thus column densities of many species are enhanced in the disk model with dust evolution, e.g., CO 2 , NH 2 CN, HNO, H 2 O, HCOOH, HCN, and CO. We also show that time-dependent chemistry is important for a proper description of gas thermal balance.

A note on dust grain charging in space plasmas

Science.gov (United States)

Rosenberg, M.; Mendis, D. A.

1992-01-01

Central to the study of dust-plasma interactions in the solar system is the electrostatic charging of dust grains. While previous calculations have generally assumed that the distributions of electrons and ions in the plasma are Maxwellian, most space plasmas are observed to have non-Maxwellian tails and can often be fit by a generalized Lorentzian (kappa) distribution. Here we use such a distribution to reevaluate the grain potential, under the condition that the dominant currents to the grain are due to electron and ion collection, as is the case in certain regions of space. The magnitude of the grain potential is found to be larger than that in a Maxwellian plasma as long as the electrons are described by a kappa distribution: this enhancement increased with ion mass and decreasing electron kappa. The modification of the grain potential in generalized Lorentzian plasmas has implications for both the physics (e.g., grain growth and disruption) and the dynamics of dust in space plasmas. These are also briefly discussed.

The water kefir grain inoculum determines the characteristics of the resulting water kefir fermentation process.

Science.gov (United States)

Laureys, D; De Vuyst, L

2017-03-01

To investigate the influence of the water kefir grain inoculum on the characteristics of the water kefir fermentation process. Three water kefir fermentation processes were started with different water kefir grain inocula and followed as a function of time regarding microbial species diversity, community dynamics, substrate consumption profile and metabolite production course. The inoculum determined the water kefir grain growth, the viable counts on the grains, the time until total carbohydrate exhaustion, the final metabolite concentrations and the microbial species diversity. There were always 2-10 lactic acid bacterial cells for every yeast cell and the majority of these micro-organisms was always present on the grains. Lactobacillus paracasei, Lactobacillus hilgardii, Lactobacillus nagelii and Saccharomyces cerevisiae were always present and may be the key micro-organisms during water kefir fermentation. Low water kefir grain growth was associated with small grains with high viable counts of micro-organisms, fast fermentation and low pH values, and was not caused by the absence of exopolysaccharide-producing lactic acid bacteria. The water kefir grain inoculum influences the microbial species diversity and characteristics of the fermentation process. A select group of key micro-organisms was always present during fermentation. This study allows a rational selection of a water kefir grain inoculum. © 2016 The Society for Applied Microbiology.

High day- and night-time temperatures affect grain growth dynamics in contrasting rice genotypes.

Science.gov (United States)

Shi, Wanju; Yin, Xinyou; Struik, Paul C; Solis, Celymar; Xie, Fangming; Schmidt, Ralf C; Huang, Min; Zou, Yingbin; Ye, Changrong; Jagadish, S V Krishna

2017-11-02

Rice grain yield and quality are predicted to be highly vulnerable to global warming. Five genotypes including heat-tolerant and susceptible checks, a heat-tolerant near-isogenic line and two hybrids were exposed to control (31 °C/23 °C, day/night), high night-time temperature (HNT; 31 °C/30 °C), high day-time temperature (HDT; 38 °C/23 °C) and high day- and night-time temperature (HNDT; 38 °C/30 °C) treatments for 20 consecutive days during the grain-filling stage. Grain-filling dynamics, starch metabolism enzymes, temporal starch accumulation patterns and the process of chalk formation were quantified. Compensation between the rate and duration of grain filling minimized the impact of HNT, but irreversible impacts on seed-set, grain filling and ultimately grain weight were recorded with HDT and HNDT. Scanning electron microscopy demonstrated irregular and smaller starch granule formation affecting amyloplast build-up with HDT and HNDT, while a quicker but normal amylopast build-up was recorded with HNT. Our findings revealed temporal variation in the starch metabolism enzymes in all three stress treatments. Changes in the enzymatic activity did not derail starch accumulation under HNT when assimilates were sufficiently available, while both sucrose supply and the conversion of sucrose into starch were affected by HDT and HNDT. The findings indicate differential mechanisms leading to high day and high night temperature stress-induced loss in yield and quality. Additional genetic improvement is needed to sustain rice productivity and quality under future climates. © Society for Experimental Biology 2017.

Towards realistic molecular dynamics simulations of grain boundary mobility

International Nuclear Information System (INIS)

Zhou, J.; Mohles, V.

2011-01-01

In order to investigate grain boundary migration by molecular dynamics (MD) simulations a new approach involving a crystal orientation-dependent driving force has been developed by imposing an appropriate driving force on grain boundary atoms and enlarging the effective range of driving force. The new approach has been validated by the work of the driving force associated with the motion of grain boundaries. With the new approach the relation between boundary migration velocity and driving force is found to be nonlinear, as was expected from rate theory for large driving forces applied in MD simulations. By evaluating grain boundary mobility nonlinearly for a set of symmetrical tilt boundaries in aluminum at high temperature, high-angle grain boundaries were shown to move much faster than low-angle grain boundaries. This agrees well with experimental findings for recrystallization and grain growth. In comparison with the available data the simulated mobility of a 38.21 o Σ7 boundary was found to be significantly lower than other MD simulation results and comparable with the experimental values. Furthermore, the average volume involved during atomic jumps for boundary migration is determined in MD simulations for the first time. The large magnitude of the volume indicates that grain boundary migration is accomplished by the correlated motion of atom groups.

The effect of feeding wheat varieties with different grain pigmentation on growth performance, texture, colour and meat sensory traits of broiler chickens

Directory of Open Access Journals (Sweden)

Ondřej Šťastník

2017-01-01

Full Text Available The feeding effect of of three spring wheat genotypes (Vánek, Konini and UC66049 with different grain colour on growth performance, body composition and meat quality parameters of broiler chickens was tested. Ninety chickens were divided into three groups (control, Konini and UC with 30 chickens in each. The tested genotypes were compares with standard variety Vánek (control with common (red grain colour. The two experimental groups received feed mixtures containing 38.2% of wheats with different grain colour: groups Konini (n = 30 and UC (n = 30 with. The third group (n = 30 had 38.2% of common wheat Vánek cultivar (Control group. The live weight of chickens between the experimental groups and control group was not significant different, as well as body composition and chemical analysis of breast and thigh meat of chickens. The feeding of wheat with different grain colour had no effect on performance parameters of broiler chickens. Breast meat tenderness according to the Razor Blade Shear Force was higher in control group against experimental groups. The colour change was not significantly different in all coordinates. pH values (measured after 1-hour post mortem were found significantly higher in the group fattening with Konini wheat than control and UC groups. Chickens meat from the experimental group was characterised by steady overall quality. The effect of various feeding had no effect on meat quality in terms of relevance to consumers.

Science at the interface : grain boundaries in nanocrystalline metals.

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, Mark Andrew; Follstaedt, David Martin; Knapp, James Arthur; Brewer, Luke N.; Holm, Elizabeth Ann; Foiles, Stephen Martin; Hattar, Khalid M.; Clark, Blythe B.; Olmsted, David L.; Medlin, Douglas L.

2009-09-01

Interfaces are a critical determinant of the full range of materials properties, especially at the nanoscale. Computational and experimental methods developed a comprehensive understanding of nanograin evolution based on a fundamental understanding of internal interfaces in nanocrystalline nickel. It has recently been shown that nanocrystals with a bi-modal grain-size distribution possess a unique combination of high-strength, ductility and wear-resistance. We performed a combined experimental and theoretical investigation of the structure and motion of internal interfaces in nanograined metal and the resulting grain evolution. The properties of grain boundaries are computed for an unprecedented range of boundaries. The presence of roughening transitions in grain boundaries is explored and related to dramatic changes in boundary mobility. Experimental observations show that abnormal grain growth in nanograined materials is unlike conventional scale material in both the level of defects and the formation of unfavored phases. Molecular dynamics simulations address the origins of some of these phenomena.

Grain weight improvement in wheat through irradiation

International Nuclear Information System (INIS)

Rasal, P.N.; Gadekar, D.A.; Gavhane, V.N.; Bhoite, K.D.

2006-01-01

T. aestivum wheat variety NIAW 34 was developed by Agricultural Research Station, Niphad, and was released by Central Varietal Release Committee, for cultivation under irrigated late sown conditions of Peninsular Zone. The grains of NIAW 34 are medium sized with 40g 1000 grain weight. However, in market the bold sized grains (above 40g 1000 grain weight) are preferred by the traders and consumers. To overcome this lacuna, grains of wheat variety NIAW 34 were irradiated to exploit the possibilities of improvement in test weight. The material was irradiated with 15 and 20 kr dose of gamma rays. In M2 generation, mutants for various morphological characters were observed. The plants showing vigorous growth habit and desirable morphological characters were selected. These selected plants were studied for grain characters after harvest. On the basis of improved test weight as compared to parental line, selections were effected. The material was advanced to M6 generation and found stable for character of interest. The material selected comprised of total 10 lines showing improved test weight having range of 42-46 g i.e. increase of 4-6 g over the parental line NIAW 34. The lines selected are being evaluated in yield evaluation trials during Rabi 2006-07. Amongst the doses used, frequency of desired mutants was higher in treatment, of 15 kr

Gene and stress history interplay in emergence of PTSD-like features.

Science.gov (United States)

Chakraborty, Nabarun; Meyerhoff, James; Gautam, Aarti; Muhie, Seid; Jibitu, Meskerem; De Lima, Thereza C M; Hammamieh, Rasha; Jett, Marti

2015-10-01

Systematically distinguishing genetic liability from other contributing factors is critical for designing a preventive strategy for post-traumatic stress disorder (PTSD). To address this issue, we investigated a murine model exposing C57BL/6j, DBA/2j and BALB/cj mice to repeated stress via exposure to conspecific aggressors (Agg-E). Naïve mice from each strain were subjected to the proximity of aggressor (Agg) mice for 6h using a 'cage-within-a-cage' paradigm, which was repeated for 5 or 10 days with intermittent and unpredictable direct contact with Agg mice. During the Agg-E stress, DBA/2j developed a different strategy to evade Agg mice, which potentially contributed to its phenotypic resilience to Agg-E stress. Although Agg mice inflicted C57BL/6j and BALB/cj with equivalent numbers of strikes, BALB/cj displayed a distinct behavioral phenotype with delayed exhibition of a number of PTSD-like features. By contrast, C57BL/6j mice displayed unique vulnerability to Agg-E stress induced myocardopathy, possibly attributable to their particular susceptibility to hypoxia. A group of genes (Bdnf, Ngf, Zwint, Cckbr, Slc6a4, Fkbp5) linked to PTSD and synaptic plasticity were significantly altered in C57BL/6j and BALB/cj Agg-E mice. Contributions of Agg-E stress history and genotypic heterogeneity emerged as the key mediators of PTSD-like features. Linking genetic components to specific phenotypic and pathological features could have potential clinical implications. Copyright © 2015 Elsevier B.V. All rights reserved.

Microhardness and grain size of disordered nonstoichiometric titanium carbide

International Nuclear Information System (INIS)

Lipatnikov, V.N.; Zueva, L.V.; Gusev, A.I.

1999-01-01

Effect of the disordered nonstoichiometric titanium carbide on its microhardness and grain size is studied. It is established that decrease in defectiveness of carbon sublattice of disordered carbide is accompanied by microhardness growth and decrease in grain size. Possible causes of the TiC y microhardness anomalous behaviour in the area 0.8 ≤ y ≤ 0.9 connected with plastic deformation mechanism conditioned by peculiarities of the electron-energetic spectrum of nonstoichiometric carbide are discussed [ru

GROWTH PERFORMANCE AND CARCASS COMPOSITION OF RABBITS FED ON DIETS OF GRADUAL LEVELS OF BARLEY GRAIN

Directory of Open Access Journals (Sweden)

M.M. El-Adawy

2012-05-01

Full Text Available Forty-eight male New Zealand White rabbits of 6 weeks age (BW 875 ± 28.3 g were randomly allocated among six groups in different levels of barley grains (BG; 0 (B0, 5 (B5, 10 (B10, 15 (B15, 20 (B20, 25% (B25 of the total diet on growth performance and carcass composition of rabbits . The highest live BW value (P < 0.05 was obtained in B20 rabbits, whereas the highest feed intake (P < 0.05 value was obtained in B25 rabbits followed by those fed on the other diets. The better-feed conversion ratio (FCR was obtained in B20 rabbits followed by those of B15 and B25. Animals of B20 had better FCR than those of the other experimental diets. The relative contribution of soft feces to dry matter or crude protein intake differed (P < 0.05 among the experimental diets. The caecal turnover rate was increased (P < 0.05 in B15 and B20 rabbits than those other diets. The per-slaughter weight, hot and cold carcass weight and dressing percentage were differed (P < 0.05 among the experimental groups and highest values were recorded in B20 rabbits. Data suggested that a partial replacement of corn grains (CG by 20% BG in rabbit diets was increased live body weight, feed intake and feed conversion ratio.

Microstructure and nanoindentation of the CLAM steel with nanocrystalline grains under Xe irradiation

Energy Technology Data Exchange (ETDEWEB)

Chang, Yongqin, E-mail: chang@ustb.edu.cn; Zhang, Jing; Li, Xiaolin; Guo, Qiang; Wan, Farong; Long, Yi

2014-12-15

This work presents an early look at irradiation effects on China low activation martensitic (CLAM) steel with nanocrystalline grains (NC-CLAM steels) under 500 keV Xe-ion bombardment at room temperature to doses up to 5.3 displacements per atom (dpa). The microstructure in the topmost region of the steel is composed of nanocrystalline grains with an average diameter of 13 nm. As the samples were implanted at low dose, the nanocrystalline grains had martensite lath structure, and many dislocations and high density bubbles were introduced into the NC-CLAM steels. As the irradiation dose up to 5.3 dpa, a tangled dislocation network exists in the lath region, and the size of the bubbles increases. X-ray diffraction results show that the crystal quality decreases after irradiation, although the nanocrystals obviously coarsen. Grain growth under irradiation may be ascribed to the direct impact of the thermal spike on grain boundaries in the NC-CLAM steels. In irradiated samples, a compressive stress exists in the surface layer because of grain growth and irradiation-introduced defects, while the irradiation introduced grain-size coarsening and defects gradients from the surface to matrix result in a tensile stress in the irradiated NC-CLAM steels. Nanoindentation was used to estimate changes in mechanical properties during irradiation, and the results show that the hardness of the NC-CLAM steels increases with increasing irradiation dose, which was ascribed to the competition between the grain boundaries and the irradiation-introduced defects.

Covalently Connecting Crystal Grains with Polyvinylammonium Carbochain Backbone To Suppress Grain Boundaries for Long-Term Stable Perovskite Solar Cells.

Science.gov (United States)

Li, Han; Liang, Chao; Liu, Yingliang; Zhang, Yiqiang; Tong, Jincheng; Zuo, Weiwei; Xu, Shengang; Shao, Guosheng; Cao, Shaokui

2017-02-22

Grain boundaries act as rapid pathways for nonradiative carrier recombination, anion migration, and water corrosion, leading to low efficiency and poor stability of organometal halide perovskite solar cells (PSCs). In this work, the strategy suppressing the crystal grain boundaries is applied to improve the photovoltaic performance, especially moisture-resistant stability, with polyvinylammonium carbochain backbone covalently connecting the perovskite crystal grains. This cationic polyelectrolyte additive serves as nucleation sites and template for crystal growth of MAPbI 3 and afterward the immobilized adjacent crystal grains grow into the continuous compact, pinhole-free perovskite layer. As a result, the unsealed PSC devices, which are fabricated under low-temperature fabrication protocol with a proper content of polymer additive PVAm·HI, currently exhibit the maximum efficiency of 16.3%. Remarkably, these unsealed devices follow an "outside-in" corrosion mechanism and respectively retain 92% and 80% of the initial PCE value after being exposed under ambient environment for 50 days and 100 days, indicating the superiority of carbochain polymer additives in solving the long-term stability problem of PSCs.

Something from nothing: self-charging of identical grains

Science.gov (United States)

Shinbrot, Troy; Yoshimatsu, Ryuta; Nuno Araujo, Nuno; Wurm, Gerhard; Herrmann, Hans

We investigate the electrostatic charging of an agitated bed of identical grains using simulations, mathematical modeling, and experiments. We simulate charging with a discrete-element model including electrical multipoles and find that infinitesimally small initial charges can grow exponentially rapidly. We propose a mathematical Turing model that defines conditions for exponential charging to occur and provides insights into the mechanisms involved. Finally, we confirm the predicted exponential growth in experiments using vibrated grains under microgravity, and we describe novel predicted spatiotemporal states that merit further study. I acknowledge support from NSF/DMR, award 1404792.

NDVI to Detect Sugarcane Aphid Injury to Grain Sorghum.

Science.gov (United States)

Elliott, N C; Backoulou, G F; Brewer, M J; Giles, K L

2015-06-01

Multispectral remote sensing has potential to provide quick and inexpensive information on sugarcane aphid, Melanaphis sacchari (Zehntner), pest status in sorghum fields. We describe a study conducted to determine if injury caused by sugarcane aphid to sorghum plants in fields of grain sorghum could be detected using multispectral remote sensing from a fixed wing aircraft. A study was conducted in commercial grain sorghum fields in the Texas Gulf Coast region in June 2014. Twenty-six commercial grain sorghum fields were selected and rated for the level of injury to sorghum plants in the field caused by sugarcane aphid. Plant growth stage ranged from 5.0 (watery ripe) to 7.0 (hard dough) among fields; and plant injury rating from sugarcane aphid ranged from 1.0 (little or no injury) to 4.0 (>40% of plants displaying injury) among fields. The normalized differenced vegetation index (NDVI) is calculated from light reflectance in the red and near-infrared wavelength bands in multispectral imagery and is a common index of plant stress. High NDVI indicates low levels of stress and low NDVI indicates high stress. NDVI ranged from -0.07 to 0.26 among fields. The correlation between NDVI and plant injury rating was negative and significant, as was the correlation between NDVI and plant growth stage. The negative correlation of NDVI with injury rating indicated that plant stress increased with increasing plant injury. Reduced NDVI with increasing plant growth probably resulted from reduced photosynthetic activity in more mature plants. The correlation between plant injury rating and plant growth stage was positive and significant indicating that plant injury from sugarcane aphid increased as plants matured. The partial correlation of NDVI with plant injury rating was negative and significant indicating that NDVI decreased with increasing plant injury after adjusting for its association with plant growth stage. We demonstrated that remotely sensed imagery acquired from grain

Design of Grain Refiners for Aluminium Alloys

Science.gov (United States)

Tronche, A.; Greer, A. L.

The efficiency of a grain refiner can be quantified as the number of grains per nucleant particle in the solidified product. Even for effective refiners in aluminium, such as Al-5Ti-1B, it is known from experiments that efficiencies are very low, at best 10-3 to 102. It is of interest to explore the reasons for such low values, and to assess the prospects for increased efficiency though design of refiners. Recently it has been shown [1] that a simple recalescence-based model can make quantitative predictions of grain size as a function of refiner addition level, cooling rate and solute content. In the model, the initiation of grains is limited by the free growth from nucleant particles, the size distribution of which is very important. The present work uses this model as the basis for discussing the effect of particle size distribution on grain refiner performance. Larger particles (of TiB2 in the case of present interest) promote greater efficiency, as do narrower size distributions. It is shown that even if the size distribution could be exactly specified, compromises would have to be made to balance efficiency (defined as above) with other desirable characteristics of a refiner.

Behavior of 14C-BHC residues in rice grain

International Nuclear Information System (INIS)

Lee, S.R.; Kim, Y.H.

1981-01-01

γ-(U- 14 C)-BHC was applied to rice plants grown in a pot and its fate in the growth, polishing and oil-extraction processes of the grain was investigated. The 14 C-activity was absorbed and translocated widely in the plant and the recovery of applied 14 C-activity in the straw and grain was about 2.8%, of which 9.4% was found in the brown rice. The % partitioning of 14 C-residues in bran and polished rice was 12:88 and that in oil and oilcake was 37:63. Characterization of 14 C-residues the presence of γ-BHC, pentachlorocyclohexene, trichlorobenzene and hydrophilic metabolites, whose proportions were different in the straw and grain. (Author)

Microstructure development in Kolmogorov, Johnson-Mehl, and Avrami nucleation and growth kinetics

Science.gov (United States)

Pineda, Eloi; Crespo, Daniel

1999-08-01

A statistical model with the ability to evaluate the microstructure developed in nucleation and growth kinetics is built in the framework of the Kolmogorov, Johnson-Mehl, and Avrami theory. A populational approach is used to compute the observed grain-size distribution. The impingement process which delays grain growth is analyzed, and the effective growth rate of each population is estimated considering the previous grain history. The proposed model is integrated for a wide range of nucleation and growth protocols, including constant nucleation, pre-existing nuclei, and intermittent nucleation with interface or diffusion-controlled grain growth. The results are compared with Monte Carlo simulations, giving quantitative agreement even in cases where previous models fail.

Effect of surface roughness on grain growth and sintering of alumina

Indian Academy of Sciences (India)

Administrator

Variation in surface roughness properties are also correlated with grain size. Rz ... ceramic product having accurate size and shape with per- fect flatness .... Figure 1. Variation in Ra with temperature: (a) fine, (b) intermediate and (c) coarse.

Influence of transport mechanisms on nucleation and grain structure formation in DC cast aluminium alloy ingots

Science.gov (United States)

Bedel, M.; Založnik, M.; Kumar, A.; Combeau, H.; Jarry, P.; Waz, E.

2012-01-01

The grain structure formation in direct chill (DC) casting is directly linked to nucleation, which is generally promoted by inoculation. Inoculation prevents defects, but also modifies the physical properties by changing the microstructure. We studied the coupling of the nucleation on inoculant particles and the grain growth in the presence of melt flow induced by thermosolutal convection and of the transport of free-floating equiaxed grains. We used a volume-averaged two-phase multiscale model with a fully coupled description of phenomena on the grain scale (nucleation on grain refiner particles and grain growth) and on the product scale (macroscopic transport). The transport of inoculant particles is also modeled, which accounts for the inhomogeneous distribution of inoculant particles in the melt. The model was applied to an industrial sized (350mm thick) DC cast aluminium alloy ingot. A discretised nuclei size distribution was defined and the impact of different macroscopic phenomena on the grain structure formation was studied: the zone and intensity of nucleation and the resulting grain size distribution. It is shown that nucleation in the presence of macroscopic transport cannot be explained only in terms of cooling rate, but variations of composition, nuclei density and grain density, all affected by transport, must be accounted for.

Film grain synthesis and its application to re-graining

Science.gov (United States)

Schallauer, Peter; Mörzinger, Roland

2006-01-01

Digital film restoration and special effects compositing require more and more automatic procedures for movie regraining. Missing or inhomogeneous grain decreases perceived quality. For the purpose of grain synthesis an existing texture synthesis algorithm has been evaluated and optimized. We show that this algorithm can produce synthetic grain which is perceptually similar to a given grain template, which has high spatial and temporal variation and which can be applied to multi-spectral images. Furthermore a re-grain application framework is proposed, which synthesises based on an input grain template artificial grain and composites this together with the original image content. Due to its modular approach this framework supports manual as well as automatic re-graining applications. Two example applications are presented, one for re-graining an entire movie and one for fully automatic re-graining of image regions produced by restoration algorithms. Low computational cost of the proposed algorithms allows application in industrial grade software.

Dust grain charging in a wake of other grains

International Nuclear Information System (INIS)

Miloch, W. J.; Block, D.

2012-01-01

The charging of dust grain in the wake of another grains in sonic and supersonic collisionless plasma flows is studied by numerical simulations. We consider two grains aligned with the flow, as well as dust chains and multiple grain arrangements. It is found that the dust charge depends significantly on the flow speed, distance between the grains, and the grain arrangement. For two and three grains aligned, the charges on downstream grains depend linearly on the flow velocity and intergrain distance. The simulations are carried out with DiP3D, a three dimensional particle-in-cell code with both electrons and ions represented as numerical particles [W. J. Miloch et al., Phys. Plasmas 17, 103703 (2010)].

Annealing behavior of a cast Mg-Gd-Y-Zr alloy with necklace fine grains developed under hot deformation

Energy Technology Data Exchange (ETDEWEB)

Yang, Yi [Educational Key Laboratory of Nonferrous Metal Materials Science and Engineering, School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Yang, Xuyue, E-mail: yangxuyue@mail.csu.edu.cn [Educational Key Laboratory of Nonferrous Metal Materials Science and Engineering, School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083 (China); Xiao, Zhenyu; Zhang, Duxiu [Educational Key Laboratory of Nonferrous Metal Materials Science and Engineering, School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Wang, Jun [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia); Sakai, Taku [UEC Tokyo (The University of Electro-Communications), Chofu, Tokyo 182-8585 (Japan)

2017-03-14

The microstructure and texture development of a cast Mg-Gd-Y-Zr alloy during hot deformation and subsequent annealing were investigated by optical microscopy (OM) and electron backscattered diffraction (EBSD) technology. Initial microstructures with partially and fully developed new fine grains (NFGs), separately attended by continuous or interrupted hot forging, were various mixed grain structures composed of NFGs in necklace and retained coarse grains. It is shown that, during annealing, the development of grain size can be divided into three stages: i.e. an incubation of grain growth, a rapid coarsening and a normal grain growth. After a long time annealing of over 10{sup 4} ks at 693 K, the average grain size for samples continuous compressed to ε=1.2 and those interrupted compressed to ε=1.6 were close. Moreover, orientations of such strain-induced fine grains were relatively randomly distributed, leading to a weakened basal texture, while the basal plane of retained coarse grains were perpendicular to the forging direction. Such texture even became weaker during subsequent annealing. The results show that the development of necklace NFGs during hot deformation can be effective for homogeneous grain refinement under subsequent annealing.

Growth, Structure and Firm Dynamics in Grain Markets: The Case of ...

African Journals Online (AJOL)

Optiplex 7010 Pro

market, firms faced with a U-shaped average cost curve will grow until they reach the ... Regulation and institutional challenges may also deter firm owners from making .... owners/managers account for only 10% of the grain traders. Women ...

The grain charging and the dust acoustic wave instability

International Nuclear Information System (INIS)

Varma, Ram K.

2001-01-01

The stability of the steady charging state of the assembly of dust grains in a plasma is analyzed using, besides the equations of continuity and momentum balance, also the equations of thermal energy balance with the grain charging terms for both the electron and ion species. The grain charging terms account for the energy exchange between the dust grains and the electron and ion fluids. The grains are taken to be immobile for the purpose of this analysis. Two limiting cases are analyzed: (i) f(≡4πn d λ D 2 a) >1 (n d is the dust number density, λ D plasma Debye length, and a, the grain radius). The steady grain charge state is found to be stable in the case f o is unaffected. On the other hand, in the limit f>>1, the state is found to be unstable provided γ q (≡q o e/aT e ) e -T i )/T e (T e , T i are electron and ion temperatures). A coherent charging of the dust grains results as a consequence of this instability until γ q ≅(1/2) (T e -T i )/T i . Next, by letting the grain charges be mobile, so that the perturbation of dust number density is nonzero, we examine the stability of the dust-acoustic wave (DAW). The DAW is found to be unstable, also in the f>>1 case, while stable in the f<<1. The instability of the DAW also implies a concomitant grain charge growth, which would again be of a coherent nature

A new insight into ductile fracture of ultrafine-grained Al-Mg alloys.

Science.gov (United States)

Yu, Hailiang; Tieu, A Kiet; Lu, Cheng; Liu, Xiong; Liu, Mao; Godbole, Ajit; Kong, Charlie; Qin, Qinghua

2015-04-08

It is well known that when coarse-grained metals undergo severe plastic deformation to be transformed into nano-grained metals, their ductility is reduced. However, there are no ductile fracture criteria developed based on grain refinement. In this paper, we propose a new relationship between ductile fracture and grain refinement during deformation, considering factors besides void nucleation and growth. Ultrafine-grained Al-Mg alloy sheets were fabricated using different rolling techniques at room and cryogenic temperatures. It is proposed for the first time that features of the microstructure near the fracture surface can be used to explain the ductile fracture post necking directly. We found that as grains are refined to a nano size which approaches the theoretical minimum achievable value, the material becomes brittle at the shear band zone. This may explain the tendency for ductile fracture in metals under plastic deformation.

On tension-compression asymmetry in ultrafine-grained and nanocrystalline metals

KAUST Repository

Gurses, Ercan

2010-12-01

We present a physically motivated computational study explaining the tension/compression (T/C) asymmetry phenomenon in nanocrystalline (nc) and ultrafine-grained (ufg) face centered cubic (fcc) metals utilizing a variational constitutive model where the nc-metal is modeled as a two-phase material consisting of a grain interior phase and a grain boundary affected zone (GBAZ). We show that the existence of voids and their growth in GBAZ renders the material pressure sensitivity due to porous plasticity and that the utilized model provides a physically sound mechanism to capture the experimentally observed T/C asymmetry in nc- and ufg-metals. © 2010 Elsevier B.V. All rights reserved.

Effects, tolerance mechanisms and management of salt stress in grain legumes.

Science.gov (United States)

Farooq, Muhammad; Gogoi, Nirmali; Hussain, Mubshar; Barthakur, Sharmistha; Paul, Sreyashi; Bharadwaj, Nandita; Migdadi, Hussein M; Alghamdi, Salem S; Siddique, Kadambot H M

2017-09-01

Salt stress is an ever-present threat to crop yields, especially in countries with irrigated agriculture. Efforts to improve salt tolerance in crop plants are vital for sustainable crop production on marginal lands to ensure future food supplies. Grain legumes are a fascinating group of plants due to their high grain protein contents and ability to fix biological nitrogen. However, the accumulation of excessive salts in soil and the use of saline groundwater are threatening legume production worldwide. Salt stress disturbs photosynthesis and hormonal regulation and causes nutritional imbalance, specific ion toxicity and osmotic effects in legumes to reduce grain yield and quality. Understanding the responses of grain legumes to salt stress and the associated tolerance mechanisms, as well as assessing management options, may help in the development of strategies to improve the performance of grain legumes under salt stress. In this manuscript, we discuss the effects, tolerance mechanisms and management of salt stress in grain legumes. The principal inferences of the review are: (i) salt stress reduces seed germination (by up to more than 50%) either by inhibiting water uptake and/or the toxic effect of ions in the embryo, (ii) salt stress reduces growth (by more than 70%), mineral uptake, and yield (by 12-100%) due to ion toxicity and reduced photosynthesis, (iii) apoplastic acidification is a good indicator of salt stress tolerance, (iv) tolerance to salt stress in grain legumes may develop through excretion and/or compartmentalization of toxic ions, increased antioxidant capacity, accumulation of compatible osmolytes, and/or hormonal regulation, (v) seed priming and nutrient management may improve salt tolerance in grain legumes, (vi) plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi may help to improve salt tolerance due to better plant nutrient availability, and (vii) the integration of screening, innovative breeding, and the development of

Grain structure evolution in Inconel 718 during selective electron beam melting

Energy Technology Data Exchange (ETDEWEB)

Helmer, H.; Bauereiß, A., E-mail: Andreas.Bauereiss@fau.de; Singer, R.F.; Körner, C.

2016-06-21

Selective electron beam melting (SEBM) is an additive manufacturing method where complex parts are built from metal powders in layers of typically 50 µm. An electron beam is used for heating (about 900 °C building temperature) and selective melting of the material. The grain structure evolution is a result of the complex thermal and hydrodynamic conditions in the melt pool. We show how different scanning strategies can be used to produce either a columnar grain structure with a high texture in building direction or an equiaxed fine grained structure. Numerical simulations of the selective melting process are applied to study the fundamental mechanisms responsible for differing grain structures. It is shown, that the direction of the thermal gradient during solidification can be altered by scanning strategies to acquire either epitaxial growth or stray grains. We show that it is possible to locally alter the grain structure of a part, thus allowing tailoring of the mechanical properties.

Grain growth control and transparency in spark plasma sintered self-doped alumina materials

International Nuclear Information System (INIS)

Suarez, M.; Fernandez, A.; Menendez, J.L.; Torrecillas, R.

2009-01-01

Doping alumina particles with aluminum alkoxides allows dense spark plasma sintered (SPSed) materials to be obtained that have a refined grain size compared to pure materials, which is critical for their transparency. An optical model considering pore and grain size distributions has been developed to obtain information about porosity in dense materials. This work suggests that the atomic diffusion mechanisms do not depend on the sintering technique. A reduction in the activation energy by a factor of 2 has been found in SPSed materials.

Breakthrough revisited: investigating the requirements for growth of dust beyond the bouncing barrier

Science.gov (United States)

Booth, Richard A.; Meru, Farzana; Lee, Man Hoi; Clarke, Cathie J.

2018-03-01

For grain growth to proceed effectively and lead to planet formation, a number of barriers to growth must be overcome. One such barrier, relevant for compact grains in the inner regions of the disc, is the `bouncing barrier' in which large grains (˜mm size) tend to bounce off each other rather than sticking. However, by maintaining a population of small grains, it has been suggested that cm-size particles may grow rapidly by sweeping up these small grains. We present the first numerically resolved investigation into the conditions under which grains may be lucky enough to grow beyond the bouncing barrier by a series of rare collisions leading to growth (so-called `breakthrough'). Our models support previous results, and show that in simple models breakthrough requires the mass ratio at which high-velocity collisions transition to growth instead of causing fragmentation to be low, ϕ ≲ 50. However, in models that take into account the dependence of the fragmentation threshold on mass ratio, we find that breakthrough occurs more readily, even if mass transfer is relatively inefficient. This suggests that bouncing may only slow down growth, rather than preventing growth beyond a threshold barrier. However, even when growth beyond the bouncing barrier is possible, radial drift will usually prevent growth to arbitrarily large sizes.

Grain-filling duration and grain yield relationships in wheat mutants

International Nuclear Information System (INIS)

Larik, A.S.

1987-01-01

Nine stable mutants of bread wheat along with their mother cultivars were investigated for grain-filling characteristics in relation to grain yield. Significant differences among mutants for grain-filling duration and grain-filling index were observed. Inspite of the consistent differences in grain-filling duration there was no significant association between grain-filling duration and grain yield in C-591 and Nayab mutants. Failure to detect an yield advantage due to differences in grain-filling duration in these genotypes suggests that any advantage derived from alteration of grain-filling period may have been outweighed by the coincident changes in length of the vegetative period. Other factors such as synchrony of anthesis may have limited out ability to find an association between grainfilling duration and grain yield. On the contrary, significant association between grain-filling duration and grain yield displayed by indus-66 indus-66 mutants derived from gamma rays, shows the ability of gamma rays to induce functional alternations in the pattern of gene arrangements controlling these traits. Thus, the vaability observed in these physiological traits suggests that selection for these traits could be useful in improving grain yield. (author)

Raising yield potential of wheat. III. Optimizing partitioning to grain while maintaining lodging resistance.

Science.gov (United States)

Foulkes, M John; Slafer, Gustavo A; Davies, William J; Berry, Pete M; Sylvester-Bradley, Roger; Martre, Pierre; Calderini, Daniel F; Griffiths, Simon; Reynolds, Matthew P

2011-01-01

A substantial increase in grain yield potential is required, along with better use of water and fertilizer, to ensure food security and environmental protection in future decades. For improvements in photosynthetic capacity to result in additional wheat yield, extra assimilates must be partitioned to developing spikes and grains and/or potential grain weight increased to accommodate the extra assimilates. At the same time, improvement in dry matter partitioning to spikes should ensure that it does not increase stem or root lodging. It is therefore crucial that improvements in structural and reproductive aspects of growth accompany increases in photosynthesis to enhance the net agronomic benefits of genetic modifications. In this article, six complementary approaches are proposed, namely: (i) optimizing developmental pattern to maximize spike fertility and grain number, (ii) optimizing spike growth to maximize grain number and dry matter harvest index, (iii) improving spike fertility through desensitizing floret abortion to environmental cues, (iv) improving potential grain size and grain filling, and (v) improving lodging resistance. Since many of the traits tackled in these approaches interact strongly, an integrative modelling approach is also proposed, to (vi) identify any trade-offs between key traits, hence to define target ideotypes in quantitative terms. The potential for genetic dissection of key traits via quantitative trait loci analysis is discussed for the efficient deployment of existing variation in breeding programmes. These proposals should maximize returns in food production from investments in increased crop biomass by increasing spike fertility, grain number per unit area and harvest index whilst optimizing the trade-offs with potential grain weight and lodging resistance.

Constitutive expression of CaPLA1 conferred enhanced growth and grain yield in transgenic rice plants.

Science.gov (United States)

Park, Ki Youl; Kim, Eun Yu; Seo, Young Sam; Kim, Woo Taek

2016-03-01

Phospholipids are not only important components of cell membranes, but participate in diverse processes in higher plants. In this study, we generated Capsicum annuum phospholipiase A1 (CaPLA1) overexpressing transgenic rice (Oryza sativa L.) plants under the control of the maize ubiquitin promoter. The T4 CaPLA1-overexpressing rice plants (Ubi:CaPLA1) had a higher root:shoot mass ratio than the wild-type plants in the vegetative stage. Leaf epidermal cells from transgenic plants had more cells than wild-type plants. Genes that code for cyclin and lipid metabolic enzymes were up-regulated in the transgenic lines. When grown under typical paddy field conditions, the transgenic plants produced more tillers, longer panicles and more branches per panicle than the wild-type plants, all of which resulted in greater grain yield. Microarray analysis suggests that gene expressions that are related with cell proliferation, lipid metabolism, and redox state were widely altered in CaPLA1-overexpressing transgenic rice plants. Ubi:CaPLA1 plants had a reduced membrane peroxidation state, as determined by malondialdehyde and conjugated diene levels and higher peroxidase activity than wild-type rice plants. Furthermore, three isoprenoid synthetic genes encoding terpenoid synthase, hydroxysteroid dehydrogenase and 3-hydroxy-3-methyl-glutaryl-CoA reductase were up-regulated in CaPLA1-overexpressing plants. We suggest that constitutive expression of CaPLA1 conferred increased grain yield with enhanced growth in transgenic rice plants by alteration of gene activities related with cell proliferation, lipid metabolism, membrane peroxidation state and isoprenoid biosynthesis.

Indices to screen for grain yield and grain-zinc mass concentrations in aerobic rice at different soil-Zn levels

NARCIS (Netherlands)

Jiang, W.; Struik, P.C.; Zhao, M.; Keulen, van H.; Fan, T.Q.; Stomph, T.J.

2008-01-01

Zinc is an important micronutrient for both crop growth and human nutrition. In rice production, yields are often reduced and Zn mass concentrations in the grains are often low when Zn is in short supply to the crop. This may result in malnutrition of people dependent on a rice-based diet. Plant

Effects of local film properties on the nucleation and growth of tin whiskers and hillocks

Science.gov (United States)

Sarobol, Pylin

Whiskers and hillocks grow spontaneously on Pb-free Sn electrodeposited films as a response to thin film stresses. Stress relaxation occurs by atom deposition to specific grain boundaries in the plane of the film, with hillocks being formed when grain boundary migration accompanies growth out of the plane of the film. The implication for whisker formation in electronics is serious: whiskers can grow to be millimeters long, sometimes causing short circuiting between adjacent components and, thereby, posing serious electrical reliability risks. In order to develop more effective whisker mitigation strategies, a predictive physics-based model has been needed. A growth model is developed, based on grain boundary faceting, localized Coble creep, as well as grain boundary sliding for whiskers, and grain boundary sliding with shear induced grain boundary migration for hillocks. In this model of whisker formation, two mechanisms are important: accretion of atoms by Coble creep on grain boundary planes normal to the growth direction inducing a grain boundary shear and grain boundary sliding in the direction of whisker growth. The model accurately captures the importance of the geometry of "surface grains"---shallow grains on film surfaces whose depths are significantly less than their in-plane grain sizes. A critical factor in the analysis is the ratio of the grain boundary sliding coefficient to the in-plane film compressive stress. If the accretion-induced shear stresses are not coupled to grain boundary motion and sliding occurs, a whisker forms. If the shear stress is coupled to grain boundary migration, a hillock forms. Based on this model, long whiskers grow from shallow surface grains with easy grain boundary sliding in the direction of growth. Other observed growth morphologies will be discussed in light of our model. Additional insights into the preferred sites for whisker and hillock growth were developed based on elastic anisotropy, local film microstructure

Microstructure Control of Barium Titanate Grain-oriented Ceramics and Their Piezoelectric Properties

International Nuclear Information System (INIS)

Mori, Rintaro; Nakashima, Koichi; Fujii, Ichiro; Wada, Satoshi; Hayashi, Hiroshi; Nagamori, Yoshitaka; Yamamoto, Yuichi

2011-01-01

The Barium titanate (BaTiO 3 , BT) [110] grain-oriented ceramics along [110] direction were prepared by a templated grain growth (TGG) method. The [110] oriented BT platelike particles (t-BT) were used as template particles. The relationship between poling treatment program and piezoelectric constant was investigated. The change in the poling conditions did not greatly influence domain size and the piezoelectric constant. The relationship between piezoelectric properties and domain size in BT grain-oriented ceramics was investigated. The smaller domain size was required to increase the piezoelectric constant.

Interstellar gas and large grains toward HD 38087

International Nuclear Information System (INIS)

Snow, T.P.; Witt, A.

1989-01-01

High-dispersion IUE spectra have been obtained of HD 38087, a star associated with reflection nebulosity where 2175 A scattering has previously been observed. The presence of 2175 A in emission implies unusually large grains, an attempt was made to see how these unusual grains may have affected the depletions of gas-phase elements onto dust in the line of sight. Even though the observed scattering region constitutes only a fraction of the total column density of dust, it is expected that the present line-of-sight analysis provides useful information on the gas and dust in the scattering nebulosity. Somewhat larger overall depletions than normal are found, and it is found that the depletions of certain elements (manganese and zinc) are enhanced relative to the normal pattern of element-to-element depletions, suggesting that grain growth has occurred with some elements sticking to grains preferentially. The molecular fraction in the line of sight is low, in accord with similar lines of sight having low far-ultraviolet extinction and large depletions. 37 refs

The effect of postprocessing on tensile property and microstructure evolution of friction stir welding aluminum alloy joint

International Nuclear Information System (INIS)

Hu, Z.L.; Wang, X.S.; Pang, Q.; Huang, F.; Qin, X.P.; Hua, L.

2015-01-01

Friction stir welding is an efficient manufacturing method for joining aluminum alloy and can dramatically reduce grain size conferring excellent plastic deformation properties. Consequently, friction stir welding is used to manufacture tailor welded blanks to optimize weight or performance in the final component. In the study, the microstructural evolution and mechanical properties of friction stir welding joint during plastic forming and subsequent heat treatment were investigated. The microstructural characteristics of the friction stir welding joints were studied by Electron Backscattered Diffraction and Transmission Electron Microscopy. The mechanical properties were evaluated by tensile and microhardness tests. It is found that the tensile and yield strengths of friction stir welding joints are significantly improved after severe plastic deformation due to the grain refinement. Following heat treatment, the strength of the friction stir welding joints significantly decrease due to the obvious abnormal grain growth. Careful attention must be given to the processing route of any friction stir welding joint intended for plastic forming, especially the annealing between forming passes. Severe plastic deforming of the friction stir welding joint leads to a high level of stored energy/dislocation density, which causes the abnormal grain growth during subsequent heat treatment, and consequently reduce the mechanical properties of the friction stir welding joint. - Highlights: • Great changes are observed in the microstructure of FSW joint after postprocessing. • Postprocessing shows great effect on the microstructure stability of FSW joint. • The weld shows more significant decrease in strength than the BM due to the AGG. • Attention must be given to the processing route of FSW joint for plastic forming

Segregation to grain boundaries in nimonic PE16 superalloy

International Nuclear Information System (INIS)

Nettleship, D.J.; Wild, R.K.

1990-01-01

Nimonic PE16 alloy is a nickel-based superalloy containing 34 wt.% iron and 16wt.% chromium with additions of molybdenum, titanium and aluminium. It is used in the fuel assembly of the UK advanced gas-cooled reactors (AGR). This component supports significant loads in service and its mechanical integrity is therefore of paramount importance. Mechanical properties may be influenced by the grain size and grain boundary composition, both of which can themselves alter during service. Scanning Auger microscopy is a well-established method for investigating grain boundaries, and has now been applied to the study of PE16. In order to expose PE16 grain boundary surfaces it is necessary to hydrogen charge samples and fracture by pulling in tension at a slow strain rate within the ultra-high vacuum chamber of the Auger microprobe. A series of casts of nimonic PE16 alloy that have received a range of thermal ageing treatments have been fractured in an intergranular manner and the grain boundary composition determined. Segregation of trace and minority elements, particularly Mo and P, has been detected at grain boundaries. Significant variations between different as-manufactured casts were observed, whilst ageing brought about the growth of chromium-rich particles on the grain boundaries. Ductile fracture in PE16 followed a path through Ti(C, N) particles. Many of these particles incorporated large amounts of sulphur. (author)

Giant grains

International Nuclear Information System (INIS)

Leitch-Devlin, M.A.; Millar, T.J.; Williams, D.A.

1976-01-01

Infrared observations of the Orion nebula have been interpreted by Rowan-Robinson (1975) to imply the existence of 'giant' grains, radius approximately 10 -2 cm, throughout a volume about a parsec in diameter. Although Rowan-Robinson's model of the nebula has been criticized and the presence of such grains in Orion is disputed, the proposition is accepted, that they exist, and in this paper situations in which giant grains could arise are examined. It is found that, while a giant-grain component to the interstellar grain density may exist, it is difficult to understand how giant grains arise to the extent apparently required by the Orion nebula model. (Auth.)

Comment on "Mitigating grain growth in binary nanocrystalline alloys through solute selection based on thermodynamic stability maps"

Czech Academy of Sciences Publication Activity Database

Lejček, Pavel; Hofmann, S.

2015-01-01

Roč. 107, Sep (2015), s. 235-237 ISSN 0927-0256 R&D Projects: GA ČR GBP108/12/G043 Institutional support: RVO:68378271 Keywords : nanocrystalline materials * grain size * grain boundary energy * grain boundary segregation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.086, year: 2015

Effect of grain refiner on intermetallic phase formation in directional solidification of 6xxx series wrought Al alloys

Energy Technology Data Exchange (ETDEWEB)

Sha, G.; O' Reilly, K.; Cantor, B. [Oxford Univ. (United Kingdom). Centre for Adv. Mat. and Composites; Hamerton, R.; Worth, J.

2000-07-01

The effect of a grain refiner on the formation of intermetallic phases in a directionally solidified (Bridgman grown) model 6xxx series wrought Al alloy has been investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). A base alloy with and without Al-Ti-B grain refiner was directionally solidified in a Bridgman furnace at growth velocities in the range of 5-120 mm/min. In both cases, the Fe-containing intermetallic phases present were found to be mainly {alpha}-AlFeSi and {beta}-AlFeSi. However, in the alloy with grain refiner solidified at 5mm/min, Al{sub 13}Fe{sub 4} was also observed. Quantitative XRD results indicated that the addition of Al-Ti-B grain refiner has a strong influence on the relative quantities of intermetallic phases forming during solidification at different growth velocities, which was also confirmed by TEM observations. TEM observations also show that depending on where the {beta}-AlFeSi particles solidified e.g. grain boundaries or triple grain junctions, the size and morphology of the particles may change dramatically. TiB{sub 2} particles were observed to nucleate {beta}-AlFeSi at low and high growth velocities in the 6xxx series Al alloys. (orig.)