Brief Communications on the Limiting Minimum Grain Sizes and Mechanism of В2→В19′→В2-Transformation during Formation of Nanocrystalline Structure in Titanium Nickelide

2021 ◽  
Author(s):  
A. N. Tyumentsev
Keyword(s):  
Titanium Nickelide ◽  
Nanocrystalline Structure ◽  
Grain Sizes

Effect of Annealing on Nanocrystalline Structure of Nb3Sn Diffusion Layers in Composites with Internal Tin Sources

2010 ◽  
Vol 297-301 ◽  
pp. 126-131 ◽  
Author(s):  
E.N. Popova ◽  
Vladimir V. Popov ◽  
E.P. Romanov ◽  
S.V. Sudareva ◽  
L.V. Elohina ◽  
...  
Keyword(s):  
Grain Size ◽  
Carrying Capacity ◽  
Nanocrystalline Structure ◽  
Diffusion Annealing ◽  
External Diameter ◽  
High Temperature Annealing ◽  
Grain Sizes ◽  
Diffusion Layers ◽  
Average Grain Size ◽  
Complete Transformation

Multifilamentary Nb3Sn-based superconducting composites manufactured by an internal-tin method have been studied by transmission (TEM) and scanning (SEM) electron microscopy. The main goal of this study is to reveal the effect of diffusion annealing regimes as well as the external diameter of the wires on the structure of nanocrystalline Nb3Sn layers (average grain size, grain size distribution, layer thickness, amount of Sn, etc.). It is demonstrated that multistep diffusion annealing results in quite a complete transformation of Nb filaments into Nb3Sn though some amount of the residual Nb remains in the filaments center. With an external diameter decrease the superconducting layers structure has been found to refine and get somewhat more uniform. An additional high-temperature annealing results in marked growth of Nb3Sn grain sizes and their scattering in sizes, which may negatively affect the current-carrying capacity of a wire.

High Tensile Ductility in Electrodeposited Bulk Nanocrystalline Ni–W Alloys

2014 ◽  
Vol 922 ◽  
pp. 497-502 ◽  
Author(s):  
Isao Matsui ◽  
Yorinobu Takigawa ◽  
Kenji Higashi
Keyword(s):  
Tensile Strength ◽  
Tensile Ductility ◽  
Nanocrystalline Structure ◽  
High Strength ◽  
Complexing Agent ◽  
Grain Sizes ◽  
Saccharin Sodium ◽  
Bulk Nanocrystalline ◽  
20 Nm ◽  
Sulfamate Bath

Bulk nanocrystalline Ni–W alloys were electrodeposited from a sulfamate bath that contained saccharin sodium as a gloss agent, and propionic acid and sodium gluconate as a complexing agent (SPG bath) to understand the tensile behavior. SPG bath with 1.0 and 5.0 g/L saccharin sodium at 45 ºC produced the bulk specimens with W content of 3.4 and 1.5 at.%, respectively. The electrodeposited alloys had a nanocrystalline structure with grain sizes of approximately 20 nm and a stronger (111) texture. The bulk nanocrystalline Ni–3.4 at.%W alloys deposited from an SPG bath with 1.0 g/L saccharin sodium exhibited a tensile strength of 1.6 GPa and tensile ductility of 1.8%. The bulk nanocrystalline Ni–1.5 at.%W alloys deposited from an SPG bath with 5.0 g/L saccharin sodium exhibited a tensile strength of 1.4 GPa and tensile ductility of 1.7%. The bulk nanocrystalline Ni–W alloys with a stronger (111) texture showed high strength and low plasticity.

Structural and Mechanical Properties of Nanostructured Fe-Mn-C Alloys Prepared by Mechanical Alloying

2018 ◽  
Vol 52 ◽  
pp. 80-87 ◽  
Author(s):  
Lounes Belaid ◽  
Meriem Bendoumia ◽  
Mohamed Dakiche ◽  
Hanane Mechri ◽  
Djaffar Dahmoun ◽  
...  
Keyword(s):  
Milling Time ◽  
Milled Powder ◽  
Nanocrystalline Structure ◽  
Hadfield Steel ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Grain Sizes ◽  
New Phase ◽  
High Manganese Austenitic Steel

The object of our research is to combine the properties of Mangalloys and nanoscale advantages in order to enhance the performance and extend the range of applications in the field of work-hardening parts such as railroad components, armor, and modern auto components. We have produced a high-manganese austenitic steel nanomaterial containing more than 12 wt% Mn, which is the level of Mn in Hadfield steel. This study experimentally determined the process of phase transitions involved in Fe–13 wt% Mn–1.2 wt% C alloy during mechano-synthesis and after subsequent annealing. The milling time ranged from 0.5 to 24 h. The unique features of the nanocrystalline structure and the changes in microstructure as a function of milling time were investigated by X-ray diffraction analysis, differential scanning calorimetry, and scanning electron microscopy coupled with EDX. The grain sizes and microstrain of the milled powder were determined. A thorough study has been done on the sample where a new phase fcc (at 24h of MA) was formed.The object of our research is to combine the properties of Mangalloys and nanoscale advantages in order to enhance the performance and extend the range of applications in the field of work-hardening parts such as railroad components, armor, and modern auto components. We have produced a high-manganese austenitic steel nanomaterial containing more than 12 wt% Mn, which is the level of Mn in Hadfield steel. This study experimentally determined the process of phase transitions involved in Fe–13 wt% Mn–1.2 wt% C alloy during mechano-synthesis and after subsequent annealing. The milling time ranged from 0.5 to 24 h. The unique features of the nanocrystalline structure and the changes in microstructure as a function of milling time were investigated by X-ray diffraction analysis, differential scanning calorimetry, and scanning electron microscopy coupled with EDX. The grain sizes and microstrain of the milled powder were determined. A thorough study has been done on the sample where a new phase fcc (at 24h of MA) was formed.

The Consolidation Behavior of L12 Phase Al3Zr & (Al+12.5at%)3Zr Powders with Nanocrystalline Structure During Spark Plasma Sintering

2001 ◽  
Vol 704 ◽  
Author(s):  
Kyoung Il Moon ◽  
Seung Chul Kim ◽  
Kyung Sub Lee
Keyword(s):  
Intermetallic Compounds ◽  
Spark Plasma Sintering ◽  
Nanocrystalline Structure ◽  
Full Density ◽  
Micro Hardness ◽  
Grain Sizes ◽  
Plasma Sintering ◽  
Metastable Structures ◽  
Spark Plasma ◽  
Nanocrystalline Microstructure

AbstractThe spark plasma sintering (SPS) of L12 phase Al3Zr and (Al+12.5at.%Cu)3Zr powders with a nanocrystalline microstructure has been studied to produce bulk intermetallic compounds which maintain metastable structures such as L12 structure and nanocrystalline microstructure. The powders were prepared by 10 h planetary ball milling (PBM). Full-density L12 (Al+12.5at.%Cu)3 Zr intermetallic compounds were obtained by SPS for 0 min. at 600°C. The smallest grain size was obtained in the specimen prepared at 600°C for 0 min., which was 20-30 nm as confirmed by TEM observation. Accordingly, the highest micro-hardness, 989.5 HV, was obtained in the specimen and this value was three times higher than those of the specimens with micro grain sizes. Full density Al3Zr intermetallics were prepared by SPS at 700°C for 0 min.. However, their crystal structure was D023 and micro-hardness was 778.1 HV. By using SPS, the sintering time can be reduced within 10 min.

The dependence of the nanostructure of magnetron sputtered Cu–Ag alloy films on composition and temperature

2007 ◽  
Vol 22 (4) ◽  
pp. 1018-1023 ◽  
Author(s):  
K. Pagh Almtoft ◽  
A.M. Ejsing ◽  
J. Bøttiger ◽  
J. Chevallier ◽  
N. Schell ◽  
...  
Keyword(s):  
Phase Formation ◽  
Nanocrystalline Structure ◽  
European Synchrotron Radiation Facility ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Alloy Films ◽  
X Ray ◽  
Grain Sizes ◽  
Experimental Findings

Cu–Ag alloy films prepared by magnetron cosputtering were characterized by using x-ray diffraction. A two-phase nanocrystalline structure of Cu grains supersaturated with Ag and Ag grains saturated with Cu was always observed. When alloying Ag with Cu or Cu with Ag, the grain sizes decreased dramatically, and the supersaturation increased with the amount of the alloying element. On annealing, the grain sizes of the Cu–Ag films increased and the solubilities decreased. To shed light on the mechanisms in play during the phase formation and subsequent phase changes, additional in situ real-time measurements were carried out using a high-intensity x-ray beam from the synchrotron at the European Synchrotron Radiation Facility in Grenoble, France. Based on the experimental findings, the phase formation and the subsequent changes during annealing are discussed.

scholarly journals Application of highly entropic coatings at simultaneous spraying of three cathodes in one cycle

2020 ◽  
Vol 97 (1) ◽  
pp. 7-17
Author(s):  
V.M. Yurov ◽  
◽  
S.A. Guchenko ◽  
E.N. Eremin ◽  
Keyword(s):  
Electron Microscope ◽  
Nanocrystalline Structure ◽  
Maximum Size ◽  
Columnar Structure ◽  
Sem Images ◽  
Grain Sizes ◽  
Erosion Coefficient ◽  
Ion Plasma ◽  
Antifriction Properties ◽  
Droplet Phase

In this work, we consider the application of highly entropic coatings while simultaneously sputtering three cathodes in a single cycle. The cathodes 12Cr15G9ND, Cu, Al were chosen as cathodes. The chemical composition of the cathodes was measured using a TESCAN MIRA 3 electron microscope. Using these cathodes, coatings were applied to polished samples of steel 45 in an NNV-6.6 I1 vacuum ion-plasma apparatus. The measurement was carried out using a MIRA 3 scanning electron microscope, an HVS-1000A microhardness tester, and a tribological research facility. SEM images show that with an increase of ×5000 or more, the droplet phase is clearly detected. The maximum size of the droplet phase reaches 12.0 μm with a variety of morphometric parameters varying, for example, in a geometry coefficient K from 0.8 to 1.0. Analysis of the coating at high magnifications (×7000 and ×20,000) without the droplet phase showed that the grain sizes of the coating are as follows: minimum — 0.23 microns, maximum — 0.65 microns (average of about 0.47 microns); while the coating structure is homogeneous. The analyzed type of structure refers to the zone of the so-called «competing texture», when a dense nanocrystalline structure is present in the lower region of the film, and a columnar structure is above it. The results of this study allow us to conclude that the simultaneous deposition of deposited cathodes of various metals (especially composite) in principle allows to obtain highly entropic coatings. Two points must be taken into account here: firstly, the number of atomized cathodes must be increased; secondly, it is necessary to take into account the values of the erosion coefficient for the cathodes used so that the atomized fluxes are equimolarly proportional. Measurements of coatings showed that the microhardness of Cu+Al+12Cr15G9ND is not inferior to ordinary steels, but of course it lags behind nanostructured coatings (30–50 GPa). The proposed coatings have antifriction properties of 3 or more times and can be used in tribological pairs.

Reflection electron microscopy of as-grown diamond surfaces

1993 ◽  
Vol 51 ◽  
pp. 1006-1007
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Electron Microscopy ◽  
Synthetic Diamond ◽  
High Energy ◽  
Dark Field ◽  
Reverse Direction ◽  
Diamond Surfaces ◽  
Grain Sizes ◽  
Synthetic Diamonds ◽  
De Beers ◽  
Reflection Electron Microscopy

It has been found that the abrasion of diamond-on-diamond depends on the crystal orientation. For a {100} face, the friction coefficient for sliding along <011> is much higher than that along <001>. For a {111} face, the abrasion along <11> is different from that in the reverse direction <>. To interpret these effects, a microcleavage mechanism was proposed in which the {100} and {111} surfaces were assumed to be composed of square-based pyramids and trigonal protrusions, respectively. Reflection electron microscopy (REM) has been applied to image the microstructures of these diamond surfaces.{111} surfaces of synthetic diamond:The synthetic diamonds used in this study were obtained from the De Beers Company. They are in the as-grown condition with grain sizes of 0.5-1 mm without chemical treatment or mechanical polishing. By selecting a strong reflected beam in the reflection high-energy electron diffraction (RHEED) pattern, the dark-field REM image of the surface is formed (Fig. 1).

Dechannealing Study of Nanocrystalline Si:H Layers Produced by High Dose Hydrogen Irradiation of Silicon Crystals

1998 ◽  
Vol 536 ◽  
Author(s):  
V. P. Popov ◽  
A. K. Gutakovsky ◽  
I. V. Antonova ◽  
K. S. Zhuravlev ◽  
E. V. Spesivtsev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Rutherford Backscattering Spectrometry ◽  
Nanocrystalline Structure ◽  
Structural Defects ◽  
High Dose ◽  
Silicon Crystals ◽  
Strong Energy ◽  
Transmission Electron ◽  
Hydrogen Implantation

AbstractA study of Si:H layers formed by high dose hydrogen implantation (up to 3x107cm-2) using pulsed beams with mean currents up 40 mA/cm2 was carried out in the present work. The Rutherford backscattering spectrometry (RBS), channeling of He ions, and transmission electron microscopy (TEM) were used to study the implanted silicon, and to identify the structural defects (a-Si islands and nanocrystallites). Implantation regimes used in this work lead to creation of the layers, which contain hydrogen concentrations higher than 15 at.% as well as the high defect concentrations. As a result, the nano- and microcavities that are created in the silicon fill with hydrogen. Annealing of this silicon removes the radiation defects and leads to a nanocrystalline structure of implanted layer. A strong energy dependence of dechanneling, connected with formation of quasi nanocrystallites, which have mutual small angle disorientation (<1.50), was found after moderate annealing in the range 200-500°C. The nanocrystalline regions are in the range of 2-4 nm were estimated on the basis of the suggested dechanneling model and transmission electron microscopy (TEM) measurements. Correlation between spectroscopic ellipsometry, visible photoluminescence, and sizes of nanocrystallites in hydrogenated nc-Si:H is observed.

Relationships Between the Friction and Viscoelastic Properties of Rubber

2000 ◽  
Vol 28 (3) ◽  
pp. 178-195 ◽  
Author(s):  
N. Amino ◽  
Y. Uchiyama
Keyword(s):  
Viscoelastic Properties ◽  
Skid Resistance ◽  
Grain Sizes ◽  
Abrasive Grain ◽  
The Coefficient Of Friction ◽  
Tan Δ ◽  
Silicone Carbide ◽  
And Storage ◽  
Wet Skid Resistance ◽  
Frequency Curves

Abstract In this study, the relationships between friction and viscoelastic properties such as loss tangent tan δ and storage modulusE′ were examined. Wet skid resistance was measured using the British Pendulum Tester. The rubber specimens were rubbed againstfive silicone carbide cloths of differing abrasive grain sizes. The viscoelastic properties of the rubber specimens were measured with a viscoelasticspectrometer. From the data on wet skid resistance and viscoelastic properties, it is found that the coefficient of friction μ varies as follows:           μ = a + b · tan δ/E′ where a and b are constants. Tan δ/E′ was related to the hysteresis term of friction, and the μ-frequency curves were compared with the tan δ/E′ –frequency curves.

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