scholarly journals Laser Heating Study of the High-Temperature Interactions in Nanograined Uranium Carbides

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5568
Author(s):  
Sanjib Chowdhury ◽  
Dario Manara ◽  
Oliver Dieste-Blanco ◽  
Davide Robba ◽  
António Pereira Gonçalves
Keyword(s):  
Grain Size ◽  
Nuclear Materials ◽  
Nuclear Fuels ◽  
Crystalline Materials ◽  
Grain Sizes ◽  
Effective Role ◽  
20 Nm ◽  
Laser Heated ◽  
Temperature Interactions

Nanograined nuclear materials are expected to have a better performance as spallation targets and nuclear fuels than conventional materials, but many basic properties of these materials are still unknown. The present work aims to contribute to their better understanding by studying the effect of grain size on the melting and solid–solid transitions of nanograined UC2−y. We laser-heated 4 nm–10 nm grain size samples with UC2−y as the main phase (but containing graphite and UO2 as impurities) under inert gas to temperatures above 3000 K, and their behavior was studied by thermal radiance spectroscopy. The UC2−y solidification point (2713(30) K) and α-UC2 to β-UC2 solid–solid transition temperature (2038(10) K) were observed to remain unchanged when compared to bulk crystalline materials with micrometer grain sizes. After melting, the composite grain size persisted at the nanoscale, from around 10 nm to 20 nm, pointing to an effective role of carbon in preventing the rapid diffusion of uranium and grain growth.

scholarly journals Role of Zn And Polyaniline In Magnetic Nanocomposites And Enhanced Arsenic Adsorption Capacity In Wastewater

2021 ◽  
Author(s):  
Tran Minh Thi ◽  
Nguyen Mau Lam ◽  
Do Khanh Tung ◽  
Nguyen Manh Nghia ◽  
Duong Quoc Van ◽  
...  
Keyword(s):  
Grain Size ◽  
Adsorption Capacity ◽  
Relative Pressure ◽  
Arsenic Adsorption ◽  
Saturation Magnetic Moment ◽  
Structure Of Nanoparticles ◽  
Bet Method ◽  
Xrd Patterns ◽  
20 Nm

Abstract Polyaniline/Fe0.90Zn0.10Fe2O4 (PANI/Zn0.10Fe2.90O4) nanocomposites were synthesized by a chemical method and an onsite polymerization method. XRD patterns showed that the Zn0.10Fe2.90O4 grain size about 12 nm, while TEM image showed grain size from 10 to 20 nm. The results of Raman spectra and DTA analyses showed that PANI participated in part of the PANI/Zn0.10Fe2.90O4 nanocomposite samples. The grain size of PANI/Zn0.10Fe2.90O4 samples measured by SEM was about 35–50 nm. These results demonstrated the shell–core structures of the nanocomposite material. The magnetization measurements at room temperature showed that in 1250 Oe magnetic field, the saturation magnetic moment of PANI/Zn0.10Fe2.90O4 samples decreased from 71.2 to 42.3 emu/g when the PANI concentration increased from 0 % to 15 %. The surface area and porous structure of nanoparticles were investigated by the BET method at 77 K and a relative pressure P/P0 of about 1. The arsenic adsorption capacity of the PANI/Zn0.10Fe2.90O4 sample with the PANI concentration of 5 % was better than that of Fe3O4 and Zn0.10Fe2.90O4 in a solution of pH 7. In the solution with pH P14, the arsenic adsorption of magnetic nanoparticles was insignificant. Due to substitution of Fe ions by Zn transition metal and coating polyaniline, these materials could be reabsorbed and reused.

scholarly journals Influence of grain size on mechanisms of plastic deformation and yield stress

2020 ◽  
Vol 2020 (1) ◽  
pp. 26-32
Author(s):  
K. M. Borysovska ◽  
◽  
Y.M. Podrezov ◽  
S.O. Firstov ◽  
◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Yield Strength ◽  
Plastic Flow ◽  
Major Influence ◽  
Entire Cross Section ◽  
Physical Yield ◽  
Grain Sizes ◽  
20 Nm ◽  
Mechanisms Of Plastic Deformation

The influence of grain size on the physical yield strength of the polycrystal is considered by the method of cellular automata. The physical yield strength of the polycrystal in this model is defined as the stress at which, the plastic deformation covers the entire cross section of the sample from one edge to another. Three mechanisms of plastic deformation are considered. The first one is an initiation of plastic flow from grain to grain by dislocation pile-ups. The second one is plastic flow in different grains independently of each other under the action of external stress and the third one is intergranular slippage. Computer simulations have shown that at large grain sizes (d > 200 nm) deformation propagates from grain to grain by initiating dislocations pile-ups, since in this case pile-ups are quite powerful and have a large effect on neighboring grains. At average values of grain size (20 nm <d <200 nm) plastic deformation occurs in the grains independently of each other, and the external strain give a major influence on plastic deformation. With further reduction of the grain sizes (d <20 nm) the main mechanism of deformation is intergranular slippage. because in grains of this size are quite large image stresses that do not allow large dislocation clusters. In small grains the image forces are quite large to prevent large dislocation pile-ups formation, but the mass and volume of grain are quite small to turn or slip its under the action of external stresses. In accordance with these mechanisms, on the calculated dependence of the physical yield strength vs grain size, there are three areas with different angles of inclination in logarithmic coordinates. Keywords: yield point, grain size, Hall―Petch low.

Dislocations in Submicron Grain Size and Nanocrystalline Copper

2000 ◽  
Vol 634 ◽  
Author(s):  
T. Ungár ◽  
G. Tichy ◽  
P. G. Sanders ◽  
J. R. Weertman
Keyword(s):  
Grain Size ◽  
Profile Analysis ◽  
Dislocation Model ◽  
X Ray Diffraction ◽  
Strain Anisotropy ◽  
Nanocrystalline Copper ◽  
X Ray ◽  
Gas Condensation ◽  
Grain Sizes ◽  
20 Nm

ABSTRACTUsing the dislocation model of strain anisotropy in X-ray diffraction peak profile analysis it is shown that in nanocrystalline copper produced by inert gas condensation dislocations are present, at least, down to average grain sizes of the order of 20 nm. Based on the analysis of the dislocation contrast factors it is suggested that with decreasing grain size the proportion of Lomer-Cottrell type dislocations increases.

Stability of Ruthenium-Silica Bilayer Structures

1994 ◽  
Vol 343 ◽  
Author(s):  
Zara Weng-Sieh ◽  
Tai. D. Nguyen ◽  
Ronald Gronsky
Keyword(s):  
Grain Size ◽  
Film Thickness ◽  
Silicon Dioxide ◽  
Grain Growth ◽  
Original Film ◽  
Grain Sizes ◽  
Transmission Electron ◽  
20 Nm ◽  
Spherical Grains ◽  
Deposited Films

ABSTRACTThe microstructural evolution of ruthenium-silicon dioxide bilayer structures upon annealing is studied using transmission electron microscopy. SiO2/Ru/SiO2 structures, with thicknesses of 2/1/2 nm, 4/2/4 nm, 8/4/8 nm, and 20/10/20 nm, are formed by magnetron sputtering and annealed at 300 or 600°C. As-deposited films have grain sizes on the order of the Ru film thickness. After annealing at 600°C, significant grain growth is observed for all thicknesses, such that the final grain sizes are approximately 3 to 20x greater than the original film thickness. The largest increase in the average Ru grain size is observed for the 2 nm thick ruthenium film possibly due to the coalescence of Ru grains. The coalescence of the Ru particles in the 1 and 2 nm thick films results in the formation of lamellar Ru grains, which disrupts the contiguity of the Ru film. In all other cases, the increase in grain size is attributed to normal grain growth, but the formation of anomalous spherical grains is also observed.

Strength and Ductility in Electrodeposited Nanocrystalline Nickel

2009 ◽  
Vol 633-634 ◽  
pp. 411-420 ◽  
Author(s):  
Heather W. Yang ◽  
Farghalli A. Mohamed
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Annealing Treatment ◽  
Average Grain Size ◽  
Annealing Twins ◽  
Grain Distribution ◽  
Small Grains ◽  
20 Nm ◽  
Strength And Ductility

Electrodeposited nanocrystalline (nc) Ni having an average grain size of 20 nm was annealed at 443 K for different holding times. An examination of the microstructure following annealing showed three important features. First, all annealed samples exhibited abnormal grain growth, which was manifested by the presence of large grains that were surrounded by regions of small grains (bimodal grain distributions). Second, annealing twins existed in the large grains of the samples that showed a bimodal grain distribution. Third, by estimating the density of annealing twin, it was found that annealing nc-Ni at 443 K resulted in a maximum twin density after 5h. Following annealing treatment, specimens with different volume fractions of twins were tested under uniaxial tension at 393 K and a strain rate of 10-4 s-1. The results showed that both strength and ductility in nc-Ni attained maximum values after annealing for 5h. The role of both bimodal grain distributions and annealing twins in enhancing ductility and strength was discussed.

The ductility of cast TiAl-based alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
M H Loretto ◽  
Z. Wu ◽  
M Q Chu ◽  
D Hu
Keyword(s):  
Grain Size ◽  
Phase Field ◽  
Heat Treating ◽  
Alloying Elements ◽  
Gamma Phase ◽  
Microstructural Refinement ◽  
Grain Sizes ◽  
Degree Of Order

ABSTRACTThe factors which influence the ductility of cast samples of TiAl-based alloys are briefly reviewed with emphasis on alloys where microstructural refinement has been used in an attempt to improve ductility. The grain size in cast samples of different TiAl-based alloys can be refined either by high additions of about 1at% boron, or by lower additions of about 0.2at%. In addition it is possible to refine the microstructure by massively transforming samples and heat treating the transformed samples in the (alpha + gamma) phase field to precipitate alpha. Significantly different ductilities are found in different alloys with similar grain sizes or with similar microstructures and the origins of the improvements in ductility and of these differences are discussed in this paper. The role of alloying elements in influencing the degree of order in alpha 2 and in turn influencing slip in alpha 2 is discussed.

scholarly journals Role of Automotive Industry in Global Warming

2019 ◽  
Vol 62 (3) ◽  
pp. 197-201
Author(s):  
Shahid Hussain Abro ◽  
Alidad Chandio ◽  
Iftikhar Ahmed Channa ◽  
Abdulaziz S. Alaboodi
Keyword(s):  
Air Pollution ◽  
Grain Size ◽  
Global Warming ◽  
Automotive Industry ◽  
High Strength ◽  
Chemical Compositions ◽  
Light Weight ◽  
Grain Sizes ◽  
Heat Treated

Global warming and air pollution by human made gases such as CO2, is mainly produced by automotive industry that results in great risk for human health. The aim of this study is to reduce the above problem by using the high strength materials with low density in the manufacturing of automotive vehicles. An approach applied here is to enhance the strength by reducing the grain size, lowering the density and increasing elongation. Four steel samples with different chemical compositions were selected. Samples were heat treated from 850 °C to 1250 °C and cooled in water. Grain size distribution was calculated using matrox inspector software and result was plotted using origin. It was found that 850 °C has lowest and 1250 °C has highest grain sizes. Strength of steel can be increased not only by adding the alloying elements but also by controlling grain size. Light weight material consumes lower fuel and emits lower CO2, thus it minimizes the global warming and air pollution.  

Atomistic Studies of Plasticity in Nanophase Metals

2000 ◽  
Vol 634 ◽  
Author(s):  
H. Van Swygenhoven ◽  
P. Derlet ◽  
A. Caro ◽  
D. Farkas ◽  
M. Caturla ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Computer Simulation ◽  
Grain Size ◽  
Grain Boundaries ◽  
Excess Enthalpy ◽  
Uniaxial Stress ◽  
Polycrystalline Materials ◽  
Triple Junctions ◽  
Grain Sizes ◽  
20 Nm

ABSTRACTMolecular dynamics computer simulation of nanocrystalline Ni and Cu with mean grain sizes ranging from 5 to 20 nm show that grain boundaries in nanocrystalline metals have structures similar to most grain boundaries found in conventional polycrystalline materials. Moreover, the excess enthalpy density in grain boundaries and triple junctions appears to be independent of grain in both, computer generated and experimental measured samples. Simulations of deformation under constant uniaxial stress demonstrate a change in deformation mechanism as function of grain size: at the smallest grain sizes all deformation is accommodated in the grain boundaries, at higher grain sizes, intragrain deformation is observed

scholarly journals Effect of Grain Size on the Hydrogen Diffusion Process in Steel Using Cellular Automaton Approach

2012 ◽  
Vol 706-709 ◽  
pp. 1568-1573 ◽  
Author(s):  
N. Yazdipour ◽  
D.P. Dunne ◽  
Elena V. Pereloma
Keyword(s):  
Grain Size ◽  
Cellular Automaton ◽  
Hydrogen Diffusion ◽  
High Strength ◽  
Hydrogen Uptake ◽  
Grain Sizes ◽  
Ca Model ◽  
Simulation Results ◽  
Do So

The role of microstructure in susceptibility to hydrogen uptake and property degradation is being evaluated using a number of high strength pipeline steels. To do so, a cellular automaton (CA) model has been used to examine the effect of grain size, as a first step in assessing the influence of microstructure. The simulation results of hydrogen diffusion into microstructures with different grain sizes are presented.

The Role of Disorder in the Magnetic Properties of Mechanically Milled Nanostructured Alloys

2001 ◽  
Vol 674 ◽  
Author(s):  
Diandra L. Leslie-Pelecky ◽  
Elaine M. Kirkpatrick ◽  
Tom Pekarek ◽  
Richard L. Schalek ◽  
Paul Shand ◽  
...  
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Spin Glass ◽  
Defect Formation ◽  
Fold Increase ◽  
Nanostructured Alloys ◽  
Glassy Behavior ◽  
Mean Grain Size ◽  
20 Nm

ABSTRACTMechanical milling provides a unique means of studying the influence of grain size and disorder on the magnetic properties of nanostructured alloys. This paper compares the role of milling in the nanostructure evolution of two ferromagnets – SmCo5 and GdAl2 – and the subsequent impact of nanostructure on magnetic properties and phase transitions. The ferromagnetic properties of SmCo5 are enhanced by short (< 2 hours) milling times, producing up to an eight-fold increase in coercivity and high remanence ratios. The coercivity increase is attributed to defect formation and strain. Additional milling increases the disorder and produces a mix of ferromagnetic and antiferromagnetic interactions that form a magnetically glassy phase. GdAl2, which changes from ferromagnetic in its crystalline form to spin-glass-like in its amorphous form, is a model system for studying the dependence of magnetically glassy behavior on grain size and disorder. Nanostructured GdAl2 with a mean grain size of 8 nm shows a combination of ferromagnetic and magnetically glassy behavior, in contrast to previous studies of nanostructured GdAl2 with a grain size of 20 nm that show only spin-glass-like behavior.

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