TY  - CONF
AU  - Grbović, Jasmina
AU  - Matović, Branko
AU  - Milovanović, S.
AU  - Andrić, V.
AU  - Umićević, Ana
AU  - Cekić, Božidar
PY  - 2007
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/12515
AB  - Despite its high cost, hafnium has been gaining wider acceptance in modern technologies. Owing to its refractory properties combined with high solubility and its positive effect on heat resistance, hafnium has been used as a component of a number of new construction materials containing d elements. Recently, the serial of intermetallic compounds formed between Hf M (M = V, Cr, Mn, Fe, Co, Ni, Cu)  have been investigated as systems interesting for hydrogen storage [1,2], able to form hydrides in hydrogen-tometal atom ratios H/M  1 at rather low temperatures (T  3000 C) and pressures or as permanent magnets [3]. In this paper, we present a study on structural properties and compound formation in the CoHf systems. The microstructure of the powders was characterized by X-ray XRD with a Siemens KRISTALOFLEKX D-500, equipped with Cu-K Ni filtrated radiation. Morphological and microanalytical characterization was carried out by SEM with a Cambridge 250 MKIII and EDS microanalysis. EDXRF measurements were performed on the EDXRF spectrometer (Canberra) with a Si(Li) semiconductor detector and annular radioisotope excitation source 109Cd. All samples were measured for a period of 22500 s under the same experimental conditions on the sample holders made of Teflon rings and Mylar foil. To obtain HfCo, HfCo3 and HfCo6, the proper amount of constituent elements were arcmelting several times in purified argon atmosphere. Since there is no JSPDS data about HfCo3, size of the unit cell is deduced from the angular positions of the diffraction lines. An assumption is made on the basis of cubic crystal system. Pattern indexing was done by means of a slide rule and the correct Miller indices are assigned to each reflection. It was found that two phases are present with the same HfCo3 composition belonging to the different space groups (215 and 204) with the different lattice edges ao1 = 5.58 Å and ao2 = 4.17 Å, respectively. By EDXRF spectrometry it was observed that Hf:Co ratio in HfCo3 is 1:3 and in Hf:Co  1:1. SEM images also confirmed the XRD and EDXRF observations. One can see that samples a) HfCo3 and b) HfCo are homogenous, while in the sample c) on the porous HfCo6 phase (dark field), there are grains of   HfCo phase (bright fields).           Further investigation involving TDPAC and SQUID technique, regarding local measurements of hyperfine fields and their magnetic properties, as well as ab-initio calculations of the electronic structure are planed in order to give a dipper insight into structure and hydriding behavior of material.
PB  - Prague : Czechoslovak Microscopy Society
C3  - 8th Multinational congress on microscopy : Proceedings
T1  - Synthesis and Characterization of Hf-Co Intermetallic Compounds
SP  - 253
EP  - 254
UR  - https://hdl.handle.net/21.15107/rcub_vinar_12515
ER  - 

@conference{
author = "Grbović, Jasmina and Matović, Branko and Milovanović, S. and Andrić, V. and Umićević, Ana and Cekić, Božidar",
year = "2007",
abstract = "Despite its high cost, hafnium has been gaining wider acceptance in modern technologies. Owing to its refractory properties combined with high solubility and its positive effect on heat resistance, hafnium has been used as a component of a number of new construction materials containing d elements. Recently, the serial of intermetallic compounds formed between Hf M (M = V, Cr, Mn, Fe, Co, Ni, Cu)  have been investigated as systems interesting for hydrogen storage [1,2], able to form hydrides in hydrogen-tometal atom ratios H/M  1 at rather low temperatures (T  3000 C) and pressures or as permanent magnets [3]. In this paper, we present a study on structural properties and compound formation in the CoHf systems. The microstructure of the powders was characterized by X-ray XRD with a Siemens KRISTALOFLEKX D-500, equipped with Cu-K Ni filtrated radiation. Morphological and microanalytical characterization was carried out by SEM with a Cambridge 250 MKIII and EDS microanalysis. EDXRF measurements were performed on the EDXRF spectrometer (Canberra) with a Si(Li) semiconductor detector and annular radioisotope excitation source 109Cd. All samples were measured for a period of 22500 s under the same experimental conditions on the sample holders made of Teflon rings and Mylar foil. To obtain HfCo, HfCo3 and HfCo6, the proper amount of constituent elements were arcmelting several times in purified argon atmosphere. Since there is no JSPDS data about HfCo3, size of the unit cell is deduced from the angular positions of the diffraction lines. An assumption is made on the basis of cubic crystal system. Pattern indexing was done by means of a slide rule and the correct Miller indices are assigned to each reflection. It was found that two phases are present with the same HfCo3 composition belonging to the different space groups (215 and 204) with the different lattice edges ao1 = 5.58 Å and ao2 = 4.17 Å, respectively. By EDXRF spectrometry it was observed that Hf:Co ratio in HfCo3 is 1:3 and in Hf:Co  1:1. SEM images also confirmed the XRD and EDXRF observations. One can see that samples a) HfCo3 and b) HfCo are homogenous, while in the sample c) on the porous HfCo6 phase (dark field), there are grains of   HfCo phase (bright fields).           Further investigation involving TDPAC and SQUID technique, regarding local measurements of hyperfine fields and their magnetic properties, as well as ab-initio calculations of the electronic structure are planed in order to give a dipper insight into structure and hydriding behavior of material.",
publisher = "Prague : Czechoslovak Microscopy Society",
journal = "8th Multinational congress on microscopy : Proceedings",
title = "Synthesis and Characterization of Hf-Co Intermetallic Compounds",
pages = "253-254",
url = "https://hdl.handle.net/21.15107/rcub_vinar_12515"
}

Grbović, J., Matović, B., Milovanović, S., Andrić, V., Umićević, A.,& Cekić, B.. (2007). Synthesis and Characterization of Hf-Co Intermetallic Compounds. in 8th Multinational congress on microscopy : Proceedings
Prague : Czechoslovak Microscopy Society., 253-254.
https://hdl.handle.net/21.15107/rcub_vinar_12515

Grbović J, Matović B, Milovanović S, Andrić V, Umićević A, Cekić B. Synthesis and Characterization of Hf-Co Intermetallic Compounds. in 8th Multinational congress on microscopy : Proceedings. 2007;:253-254.
https://hdl.handle.net/21.15107/rcub_vinar_12515 .

Grbović, Jasmina, Matović, Branko, Milovanović, S., Andrić, V., Umićević, Ana, Cekić, Božidar, "Synthesis and Characterization of Hf-Co Intermetallic Compounds" in 8th Multinational congress on microscopy : Proceedings (2007):253-254,
https://hdl.handle.net/21.15107/rcub_vinar_12515 .

TY  - JOUR
AU  - Umićević, Ana
AU  - Mahnke, Heinz-Eberhard
AU  - Cekić, Božidar Đ.
AU  - Grbović, Jasmina
AU  - Koteski, Vasil J.
AU  - Belošević-Čavor, Jelena
PY  - 2006
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/6610
AB  - The alloying and phase formation in Ni-Hf samples with 0.2-, 2-, and 5-at.% Hf were studied by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). Both characterization methods, XRD and SEM, reveal the presence of the HfNi5 phase (fee structure) where the excess Ni atoms are present in the form of Ni or Ni-rich segregations in the sample containing 5-at.% Hf. The sample with 2-at.% Hf is characterized by the presence of the two phases present in the 5-at.% sample and by Hf atoms, which occupy substitutional lattice positions in the Ni lattice. Finally, in the third sample with 0.2-at.% Hf, the Hf atoms mainly substitute the Ni atoms in the lattice. This analysis is being complemented with additional information on the local structure around Hf by extended X-ray absorption fine structure spectroscopy (EXAFS).
T2  - Materials Science Forum
T1  - SEM and XRD characterization of Ni-Hf alloys at low Hf concentration
VL  - 518
SP  - 325
EP  - 330
DO  - 10.4028/www.scientific.net/msf.518.325
UR  - https://hdl.handle.net/21.15107/rcub_vinar_6610
ER  - 

@article{
author = "Umićević, Ana and Mahnke, Heinz-Eberhard and Cekić, Božidar Đ. and Grbović, Jasmina and Koteski, Vasil J. and Belošević-Čavor, Jelena",
year = "2006",
abstract = "The alloying and phase formation in Ni-Hf samples with 0.2-, 2-, and 5-at.% Hf were studied by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). Both characterization methods, XRD and SEM, reveal the presence of the HfNi5 phase (fee structure) where the excess Ni atoms are present in the form of Ni or Ni-rich segregations in the sample containing 5-at.% Hf. The sample with 2-at.% Hf is characterized by the presence of the two phases present in the 5-at.% sample and by Hf atoms, which occupy substitutional lattice positions in the Ni lattice. Finally, in the third sample with 0.2-at.% Hf, the Hf atoms mainly substitute the Ni atoms in the lattice. This analysis is being complemented with additional information on the local structure around Hf by extended X-ray absorption fine structure spectroscopy (EXAFS).",
journal = "Materials Science Forum",
title = "SEM and XRD characterization of Ni-Hf alloys at low Hf concentration",
volume = "518",
pages = "325-330",
doi = "10.4028/www.scientific.net/msf.518.325",
url = "https://hdl.handle.net/21.15107/rcub_vinar_6610"
}

Umićević, A., Mahnke, H., Cekić, B. Đ., Grbović, J., Koteski, V. J.,& Belošević-Čavor, J.. (2006). SEM and XRD characterization of Ni-Hf alloys at low Hf concentration. in Materials Science Forum, 518, 325-330.
https://doi.org/10.4028/www.scientific.net/msf.518.325
https://hdl.handle.net/21.15107/rcub_vinar_6610

Umićević A, Mahnke H, Cekić BĐ, Grbović J, Koteski VJ, Belošević-Čavor J. SEM and XRD characterization of Ni-Hf alloys at low Hf concentration. in Materials Science Forum. 2006;518:325-330.
doi:10.4028/www.scientific.net/msf.518.325
https://hdl.handle.net/21.15107/rcub_vinar_6610 .

Umićević, Ana, Mahnke, Heinz-Eberhard, Cekić, Božidar Đ., Grbović, Jasmina, Koteski, Vasil J., Belošević-Čavor, Jelena, "SEM and XRD characterization of Ni-Hf alloys at low Hf concentration" in Materials Science Forum, 518 (2006):325-330,
https://doi.org/10.4028/www.scientific.net/msf.518.325 .,
https://hdl.handle.net/21.15107/rcub_vinar_6610 .