A new synthesis route for the production of bulk nanostructured materials is presented.
Fine Ni powder was made by selected appropriate electrolysis conditions. A
compact material with an average grain size below 40 nm was obtained by subsequent
cold pressing. Then, using the high pressure torsion (HPT) deformation technique dense
bulk nanocrystalline Ni was achieved. The detailed structural investigations of the asprepared
and HPT deformed Ni powder, including X-ray diffraction (XRD) and transmission
electron microscopy (TEM), reveal in both cases the presence of a face centered
cubic (FCC) phase without presence of any oxides. Coherently scattering domain size
measurements by XRD show a value of 24 nm for the as-deposited powder and an even
smaller value of 13.5 nm after HPT deformation. In addition, optical emission spectroscopy
was employed to determine the impurity content of the obtained nanostructured
material, showing a relatively low content of 0.9 % carbon and oxygen. The microhardness
increased after deformation from (1.5 ± 0.08) GPa for the as-deposited Ni powder
to (6.6 ± 0.2) GPa for the HPT deformed Ni powder.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2061

Gammer, C.

Gavrilovic, A.

Karnthaler, H.P.

Kleber, C.

Rafailovic, L.D.

Rentenberger, C.

SocioEconomic Challenges Journal (Sumy State University)

Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part II                  279 
 
HIGH PRESSURE TORSION OF NICKEL POWDERS OB-
TAINED BY ELECTRODEPOSITION 
Lidija D. Rafailovi?1,2, Christian Rentenberger2, Aleksandra Gavrilovi?1,  
Christoph Kleber1,  Hans Peter Karnthaler2, Christoph Gammer2 
 
1 CEST, Center of Electrochemical Surface Technology, Viktor-Kaplan- Straße 2, 2700 Wr. 
Neustadt, Austria 
2 Faculty of Physics, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Vienna, 
Austria 
 
ABSTRACT 
A new synthesis route for the production of bulk nanostructured materials is pre-
sented. Fine Ni powder was made by selected appropriate electrolysis conditions. A 
compact material with an average grain size below 40 nm was obtained by subsequent 
cold pressing. Then, using the high pressure torsion (HPT) deformation technique dense 
bulk nanocrystalline Ni was achieved. The detailed structural investigations of the as-
prepared and HPT deformed Ni powder, including X-ray diffraction (XRD) and trans-
mission electron microscopy (TEM), reveal in both cases the presence of a face centered 
cubic (FCC) phase without presence of any oxides. Coherently scattering domain size 
measurements by XRD show a value of 24 nm for the as-deposited powder and an even 
smaller value of 13.5 nm after HPT deformation. In addition, optical emission spectros-
copy was employed to determine the impurity content of the obtained nanostructured 
material, showing a relatively low content of 0.9 % carbon and oxygen. The microhard-
ness increased after deformation from (1.5 ± 0.08) GPa for the as-deposited Ni powder 
to (6.6 ± 0.2) GPa for the HPT deformed Ni powder.  
 
Key words: electrodeposition, high pressure torsion, powder consolidation, hard-
ness, bulk nanocrystalline Ni. 
 
INTRODUCTION 
Bulk nanocrystalline metals containing a large volume of grain boundaries 
receive increasing interest since they often show improved mechanical proper-
ties as high strength combined with high ductility [1]. Bulk metals are frequent-
ly made nanocrystalline using a top down approach (e.g. high pressure torsion 
[2-3]), but the final grain size that can be reached is limited. On the other hand 
bottom up approaches (e.g. electrodeposition [4]) allow the production of nano-
crystalline metals with considerable smaller grain sizes, but the resulting mate-
rial is present in the form of powders or thin films.  
METHODS OF SAMPLE MANUFACTURING AND ANALYSIS 
Ni powders were obtained galvanostatically at a selected high constant cur-
rent density. As-deposited powders, compactified by cold pressing and deformed 
280                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part II           
 
by HPT at room temperature under a hydrostatic pressure of 8 GPa (Fig. 1) were 
systematically studied by X-ray diffraction analysis and TEM methods.  
The impurity content 
was determined by optical 
emission spectroscopy. 
RESULTS AND 
DISCUSSION 
Figure 2 shows X-ray 
diffraction patterns of the 
as-deposited and the HPT 
deformed Ni powder. Co-
herently scattering domain 
size measurements by 
XRD revealed a value of 24 nm for the as-deposited powder. By the subsequent 
HPT deformation, the coherently scattering domain size was decreased even 
further to 13.5 nm. 
The low content of 
impurities and the ab-
sence of oxides are cru-
cial for the mechanical 
properties as impurities 
would cause embrittle-
ment in the material. 
Glow discharge optical 
emission spectroscopy 
shows a composition of 
99.1 at.% of Ni and 0.9 
at.% O and C. The TEM 
study (Fig.  3)  shows  a  
comparable grain-size of 
around 35 nm for the as-deposited and HPT deformed Ni powder.   
 
Fig. 3 – Dark field images of (a) as-deposited and (b) HPT deformed Ni powder. The 
grain size of both samples is comparable (35 nm), but the HPT deformed sample con-
tains a high density of dislocations. 
 
Fig. 1 –  Sketch  of  the  HPT  
deformation technique. The 
upper and the lower plunger 
(grey, cylindrical) are pressed 
against the disk-shaped sam-
ple (black). The lower anvil is 
rotated against the upper one, 
leading to a torsional defor-
mation in the sample 
 
Fig. 2 – X-ray profiles of as-deposited and HPT  
deformed Ni powder, showing the presence of FCC  
Ni only. 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part II                  281 
 
Due  to  the  small  grain  size  a  very  high  microhardness  of  6.6  GPa  was  
achieved in the case of the HPT deformed Ni powder. 
CONCLUSIONS 
We show that by combining electrodeposition and HPT deformation it is 
possible to obtain dense bulk specimens with small grain sizes. Preliminary 
results obtained by XRD and TEM analysis show that the very fine grain size 
of the as-deposited powder (35 nm) is preserved after HPT deformation. The 
coherently scattering domain size is reduced during the HPT deformation due 
to the generation of dislocations in the sample. The small grain size and high 
dislocation density in the achieved specimen leads to an enhanced microhard-
ness.  It can be concluded that the combination of electrodeposition and HPT 
deformation presents a new route for synthesizing bulk nanostructued metals. A 
dense specimen with a low content of impurities, a very small grain size and 
improved mechanical properties was achieved. 
 
Acknowledgements 
This research was supported by the research project “Bulk Nanostructured 
Materials” within the research focus “Material Science” of the University of 
Vienna and by the Austrian Science Fund (FWF): [S10403, P22440]. The work at 
CEST was supported within the COMET program by the Austrian Research 
Promotion Agency (Österreichische Forschungsförderungsgesellschaft, FFG) and 
the government of Lower Austria. 
REFERENCES 
[1] H. Gleiter, Acta Mater, 2000, Vol.48, P.1-29. 
[2] R.Z. Valiev, Y. Estrin, Z. Horita, T.G. Langdon, M.J. Zehetbauer, Y.T. Zhu, JOM 
2006, Vol.58(4), P.33-9.  
[3] C.  Mangler,  C.  Gammer,  H.  P.  Karnthaler,  C.  Rentenberger,  Acta  Mater,  2010,  
Vol.58, P.5631-5638. 
[4] L. D. Rafailovic, D. M. Minic, H. P. Karnthaler, J. Wosik, T. Trisovic, G. E. Nauer, 
J Electrochem Soc, 2010, Vol.157, P.295-D301. 
 
  


English

High pressure torsion of nickel powders obtained by electrodeposition

Electronic Sumy State University Institutional Repository

Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part II                  279  HIGH PRESSURE TORSION OF NICKEL POWDERS OB-TAINED BY ELECTRODEPOSITION Lidija D. Rafailoviü1,2, Christian Rentenberger2, Aleksandra Gavriloviü1,  Christoph Kleber1,  Hans Peter Karnthaler2, Christoph Gammer2  1 CEST, Center of Electrochemical Surface Technology, Viktor-Kaplan- Straße 2, 2700 Wr. Neustadt, Austria 2 Faculty of Physics, Physics of Nanostructured Materials, Boltzmanngasse 5, 1090 Vienna, Austria  ABSTRACT A new synthesis route for the production of bulk nanostructured materials is pre-sented. Fine Ni powder was made by selected appropriate electrolysis conditions. A compact material with an average grain size below 40 nm was obtained by subsequent cold pressing. Then, using the high pressure torsion (HPT) deformation technique dense bulk nanocrystalline Ni was achieved. The detailed structural investigations of the as-prepared and HPT deformed Ni powder, including X-ray diffraction (XRD) and trans-mission electron microscopy (TEM), reveal in both cases the presence of a face centered cubic (FCC) phase without presence of any oxides. Coherently scattering domain size measurements by XRD show a value of 24 nm for the as-deposited powder and an even smaller value of 13.5 nm after HPT deformation. In addition, optical emission spectros-copy was employed to determine the impurity content of the obtained nanostructured material, showing a relatively low content of 0.9 % carbon and oxygen. The microhard-ness increased after deformation from (1.5 ± 0.08) GPa for the as-deposited Ni powder to (6.6 ± 0.2) GPa for the HPT deformed Ni powder.   Key words: electrodeposition, high pressure torsion, powder consolidation, hard-ness, bulk nanocrystalline Ni.  INTRODUCTION Bulk nanocrystalline metals containing a large volume of grain boundaries receive increasing interest since they often show improved mechanical proper-ties as high strength combined with high ductility [1]. Bulk metals are frequent-ly made nanocrystalline using a top down approach (e.g. high pressure torsion [2-3]), but the final grain size that can be reached is limited. On the other hand bottom up approaches (e.g. electrodeposition [4]) allow the production of nano-crystalline metals with considerable smaller grain sizes, but the resulting mate-rial is present in the form of powders or thin films.  METHODS OF SAMPLE MANUFACTURING AND ANALYSIS Ni powders were obtained galvanostatically at a selected high constant cur-rent density. As-deposited powders, compactified by cold pressing and deformed 280                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part II            by HPT at room temperature under a hydrostatic pressure of 8 GPa (Fig. 1) were systematically studied by X-ray diffraction analysis and TEM methods.  The impurity content was determined by optical emission spectroscopy. RESULTS AND DISCUSSION Figure 2 shows X-ray diffraction patterns of the as-deposited and the HPT deformed Ni powder. Co-herently scattering domain size measurements by XRD revealed a value of 24 nm for the as-deposited powder. By the subsequent HPT deformation, the coherently scattering domain size was decreased even further to 13.5 nm. The low content of impurities and the ab-sence of oxides are cru-cial for the mechanical properties as impurities would cause embrittle-ment in the material. Glow discharge optical emission spectroscopy shows a composition of 99.1 at.% of Ni and 0.9 at.% O and C. The TEM study (Fig.  3)  shows  a  comparable grain-size of around 35 nm for the as-deposited and HPT deformed Ni powder.    Fig. 3 – Dark field images of (a) as-deposited and (b) HPT deformed Ni powder. The grain size of both samples is comparable (35 nm), but the HPT deformed sample con-tains a high density of dislocations.  Fig. 1 –  Sketch  of  the  HPT  deformation technique. The upper and the lower plunger (grey, cylindrical) are pressed against the disk-shaped sam-ple (black). The lower anvil is rotated against the upper one, leading to a torsional defor-mation in the sample  Fig. 2 – X-ray profiles of as-deposited and HPT  deformed Ni powder, showing the presence of FCC  Ni only. Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part II                  281  Due  to  the  small  grain  size  a  very  high  microhardness  of  6.6  GPa  was  achieved in the case of the HPT deformed Ni powder. CONCLUSIONS We show that by combining electrodeposition and HPT deformation it is possible to obtain dense bulk specimens with small grain sizes. Preliminary results obtained by XRD and TEM analysis show that the very fine grain size of the as-deposited powder (35 nm) is preserved after HPT deformation. The coherently scattering domain size is reduced during the HPT deformation due to the generation of dislocations in the sample. The small grain size and high dislocation density in the achieved specimen leads to an enhanced microhard-ness.  It can be concluded that the combination of electrodeposition and HPT deformation presents a new route for synthesizing bulk nanostructued metals. A dense specimen with a low content of impurities, a very small grain size and improved mechanical properties was achieved.  Acknowledgements This research was supported by the research project “Bulk Nanostructured Materials” within the research focus “Material Science” of the University of Vienna and by the Austrian Science Fund (FWF): [S10403, P22440]. The work at CEST was supported within the COMET program by the Austrian Research Promotion Agency (Österreichische Forschungsförderungsgesellschaft, FFG) and the government of Lower Austria. REFERENCES [1] H. Gleiter, Acta Mater, 2000, Vol.48, P.1-29. [2] R.Z. Valiev, Y. Estrin, Z. Horita, T.G. Langdon, M.J. Zehetbauer, Y.T. Zhu, JOM 2006, Vol.58(4), P.33-9.  [3] C.  Mangler,  C.  Gammer,  H.  P.  Karnthaler,  C.  Rentenberger,  Acta  Mater,  2010,  Vol.58, P.5631-5638. [4] L. D. Rafailovic, D. M. Minic, H. P. Karnthaler, J. Wosik, T. Trisovic, G. E. Nauer, J Electrochem Soc, 2010, Vol.157, P.295-D301.    

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High pressure torsion of nickel powders obtained by electrodeposition

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