scholarly journals Microstructural Investigation of Nanocrystalline Hydrogen-Storing Mg-Titanate Nanotube Composites Processed by High-Pressure Torsion

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 563 ◽  
Author(s):  
Marcell Gajdics ◽  
Tony Spassov ◽  
Viktória Kovács Kis ◽  
Ferenc Béke ◽  
Zoltán Novák ◽  
...  
Keyword(s):  
High Pressure ◽  
Ball Milling ◽  
High Pressure Torsion ◽  
High Energy ◽  
Titanate Nanotubes ◽  
Microstructural Investigation ◽  
Microstructural Parameters ◽  
Preparation Conditions ◽  
Average Dislocation Density ◽  
Nanotube Composites

A high-energy ball milling and subsequent high-pressure torsion method was applied to synthesize nanocrystalline magnesium samples catalyzed by TiO2 or titanate nanotubes. The microstructure of the as-milled powders and the torqued bulk disks was characterized by X-ray diffraction. The recorded diffractograms have been evaluated by the convolutional multiple whole profile fitting algorithm, which provided microstructural parameters (average crystal size, crystallite size distribution, average dislocation density). The morphology of the nanotube-containing disks has been examined by high-resolution transmission electron microscopy. The effect of the different additives and preparation conditions on the hydrogen absorption behavior was investigated in a Sieverts’-type apparatus. It was found that the ball-milling route has a prominent effect on the dispersion and morphology of the titanate nanotubes, and the absorption capability of the Mg-based composite is highly dependent on these features.

The Influence of Preparation Conditions on the Hydrogen Sorption of Mg-Nb2O5-CNT Produced by Ball Milling and Subsequent High-Pressure Torsion

2020 ◽  
Vol 20 (7) ◽  
pp. 4587-4590 ◽  
Author(s):  
Ádám Révész ◽  
Tony Spassov ◽  
Viktória Kovács Kis ◽  
Erhard Schafler ◽  
Marcell Gajdics
Keyword(s):  
High Pressure ◽  
Ball Milling ◽  
High Pressure Torsion ◽  
High Energy ◽  
Hydrogen Sorption ◽  
Sorption Behavior ◽  
X Ray Diffraction ◽  
Preparation Conditions ◽  
Transmission Electron ◽  
Energy Ball

High energy ball milling and subsequent high-pressure torsion method was carried out on nanocrystalline Mg powders catalyzed by 5 wt.% Nb2O5 and 5 wt.% carbon nanotubes. In the present research two distinct milling routes were performed in order to reveal the influence of the processing conditions on the hydrogenation behavior of the investigated alloys. The hydrogen sorption behavior of the milled powders and the bulk disks was examined in a Sieverts’-type apparatus. Structural characterization of the catalyzed Mg powders and disks has been carried out by high-resolution transmission electron microscopy and X-ray diffraction.

scholarly journals Structural and hydrogen storage characterization of nanocrystalline magnesium synthesized by ECAP and catalyzed by different nanotube additives

2021 ◽  
Vol 60 (1) ◽  
pp. 884-893
Author(s):  
Ádám Révész ◽  
Dániel G. Fodor ◽  
György Krállics ◽  
Tony Spassov ◽  
Marcell Gajdics
Keyword(s):  
Average Crystallite Size ◽  
Hydrogen Desorption ◽  
Titanate Nanotubes ◽  
X Ray Diffraction ◽  
Microstructural Characteristics ◽  
Microstructural Parameters ◽  
Storage Performance ◽  
Average Dislocation Density ◽  
Angular Pressing

Abstract Ball-milled nanocrystalline Mg powders catalyzed by TiO2 powder, titanate nanotubes and carbon nanotubes were subjected to intense plastic deformation by equal-channel angular pressing. Microstructural characteristics of these nanocomposites have been investigated by X-ray diffraction. Microstructural parameters, such as the average crystallite size, the average dislocation density and the average dislocation distance have been determined by the modified Williamson–Hall analysis. Complementary hydrogen desorption and absorption experiments were carried out in a Sieverts’ type apparatus. It was found that the Mg-based composite catalyzed by titanate nanotubes exhibits the best overall H-storage performance, reaching 7.1 wt% capacity. The hydrogenation kinetic curves can be fitted by the contracting volume function for all the investigated materials. From the fitted parameters, it is confirmed that the titanate nanotube additive results in far the best kinetic behavior, including the highest hydride front velocity.

scholarly journals Crystallization of Cu60Zr20Ti20 bulk metallic glass by high pressure torsion

2019 ◽  
Vol 58 (1) ◽  
pp. 304-312
Author(s):  
Ádám Révész ◽  
András Horváth ◽  
Gábor Ribárik ◽  
Erhard Schafler ◽  
David J. Browne ◽  
...  
Keyword(s):  
High Pressure ◽  
Metallic Glass ◽  
Crystallite Size ◽  
Bulk Metallic Glass ◽  
High Pressure Torsion ◽  
Average Crystallite Size ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Microstructural Parameters ◽  
Profile Fitting

Abstract Bulk metallic glass of Cu60Zr20Ti20 composition has been synthesized by copper mold casting. Slices of the as-cast glass has been subjected to severe plastic deformation by high-pressure torsion for different whole turns. The microstructure and the thermal behavior of the deformed disks have been investigated by X-ray diffraction and differential scanning calorimetry. It was confirmed that the initial compression preceding the high pressure torsion induces crystallized structure, which shows only minor further changes upon the severe plastic shear deformation achieved by twisting the sample. The X-ray line profiles have been evaluated by the Convolutional Whole Profile Fitting algorithm in order to determine the evolution of the microstructural parameters, such as the median and variance of the crystallite size distribution, average crystallite size and dislocation density as a function of the number of revolutions. Hardness measurements by nanoindentation have also been carried out on the as-cast alloys and the deformed disks.

scholarly journals New Mg–V–Cr BCC Alloys Synthesized by High-Pressure Torsion and Ball Milling

2018 ◽  
Vol 59 (5) ◽  
pp. 741-746 ◽  
Author(s):  
Keisuke Fujiwara ◽  
Ryoko Uehiro ◽  
Kaveh Edalati ◽  
Hai-Wen Li ◽  
Ricardo Floriano ◽  
...  
Keyword(s):  
High Pressure ◽  
Ball Milling ◽  
High Pressure Torsion

scholarly journals Mechanochemistry of Metal Hydrides: Recent Advances

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2778 ◽  
Author(s):  
Jacques Huot ◽  
Fermín Cuevas ◽  
Stefano Deledda ◽  
Kaveh Edalati ◽  
Yaroslav Filinchuk ◽  
...  
Keyword(s):  
Ball Milling ◽  
High Pressure Torsion ◽  
International Workshop ◽  
Metal Hydrides ◽  
High Energy ◽  
Surface Mechanical Attrition Treatment ◽  
X Ray Diffraction ◽  
Mechanical Attrition ◽  
Recent Developments

This paper is a collection of selected contributions of the 1st International Workshop on Mechanochemistry of Metal Hydrides that was held in Oslo in May 2018. In this paper, the recent developments in the use of mechanochemistry to synthesize and modify metal hydrides are reviewed. A special emphasis is made on new techniques beside the traditional way of ball milling. High energy milling, ball milling under hydrogen reactive gas, cryomilling and severe plastic deformation techniques such as High-Pressure Torsion (HPT), Surface Mechanical Attrition Treatment (SMAT) and cold rolling are discussed. The new characterization method of in-situ X-ray diffraction during milling is described.

scholarly journals Quenching ilmenite with a high-temperature and high-pressure phase using super-high-energy ball milling

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Takeshi Hashishin ◽  
Zhenquan Tan ◽  
Kazuhiro Yamamoto ◽  
Nan Qiu ◽  
Jungeum Kim ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Ball Milling ◽  
High Energy ◽  
High Energy Ball Milling ◽  
High Pressure Phase ◽  
Energy Ball ◽  
Pressure Phase

Strengthening of Nickel Deformed by High Pressure Torsion

2008 ◽  
Vol 584-586 ◽  
pp. 417-421 ◽  
Author(s):  
Hong Wang Zhang ◽  
X. Huang ◽  
Niels Hansen ◽  
Reinhard Pippan ◽  
Michael Zehetbauer
Keyword(s):  
High Pressure ◽  
Cold Rolling ◽  
High Pressure Torsion ◽  
Structural Evolution ◽  
Longitudinal Section ◽  
High Angle ◽  
Microstructural Parameters ◽  
Transmission Electron ◽  
Structure Relationship ◽  
Von Mises

The strength of a deformed metal depends on the content of high angle boundaries, low angle dislocation boundaries and the dislocations between the boundaries. High angle boundaries contribute by Hall-Petch strengthening, whereas for the low angle dislocation boundaries and dislocations between boundaries the strengthening is proportional to the square root of the dislocation density. Based on an assumption of additivity of these contributions, the flow stresses of metals deformed by cold rolling have been calculated successfully. In the present investigation pure Ni (99.9%) has been deformed by high pressure torsion (HPT) to von Mises strains of 0.9, 1.7, 8.7 and 12. The strength of the HPT Ni has been determined by Vickers microhardness (HV) measurements and the microstructural parameters have been determined by transmission electron microscope (TEM) in the longitudinal section. HPT has been compared with deformation by cold rolling and torsion based on the structural evolution with strain and the stress-structure relationship. Based on an assumption of a linear additivity of boundary strengthening and dislocation strengthening, good agreement has been found between the calculated and the experimental flow stress.

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