Ni/NiO nanopowders with different metal and oxide phase ratio have been prepared by using thermal decomposition of nickel acetate ammine complexes which contain various ammonia concentrations at the temperature range 300 – 500 ºC in air. Obtained powders have been characterized by IR-spectroscopy, XRD and TG, DTA, DTG, TEM, laser granulometry, adsorption-structural method and layer-by-layer Auger analysis. Thermal decomposition of nickel ammine complexes occurred with formation of crystalline hydroxide containing and amorphous carbonate containing precursors. Changing of precursors composition with different NH3 content and annealing duration and temperature leads to different pore structure, agglomerate size of powders and determinates free and fixed carbon concentrations. Mean crystallite size of nickel depended on temperature only. In the temperature range from 350 to 500 °С the crystallite size of nickel has grown from 50 to 55 nm. Mean crystallite size of nickel oxide depended on temperature and ammonia content. In the temperature range from 350 to 500 °С the crystallite size of NiO has grown from 5 to 25 nm. Increasing ammonia content from 3.6 to 14.4 mol/mol Ni led to decreasing NiO crystallite size from 8–10 to 5 nm

Dulina, I.O.

Klochkov, L.O.

Lobunets, T.F.

Ragulya, A.V.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 3 No 2, 02NNPT02(4pp) (2014)   2304-1862/2014/3(2)02NNPT02(4) 02NNPT02-1  2014 Sumy State University Features of Ni / NiO Nanopowder Synthesis by Thermal Decomposition of Nickel Acetate Amines: Effect of Annealing Temperature and Duration and Ammonia Content on Powder Composition and Particle Size  I.O. Dulina*, T.F. Lobunets, L.O. Klochkov, A.V. Ragulya  Frantsevich Institute for Problems of Materials Science of NASU, 3, Krzhyzhanovsky Str., 03142 Kyiv, Ukraine  (Received 02 May 2014; published online 29 August 2014)  Ni/NiO nanopowders with different metal and oxide phase ratio have been prepared by using thermal decomposition of nickel acetate ammine complexes which contain various ammonia concentrations at the temperature range 300-500 ºC in air. Obtained powders have been characterized by IR-spectroscopy, XRD and TG, DTA, DTG, TEM, laser granulometry, adsorption-structural method and layer-by-layer Auger analysis. Thermal decomposition of nickel ammine complexes occurred with formation of crystalline hy-droxide containing and amorphous carbonate containing precursors. Changing of precursors composition with different NH3 content and annealing duration and temperature leads to different pore structure, ag-glomerate size of powders and determinates free and fixed carbon concentrations. Mean crystallite size of nickel depended on temperature only. In the temperature range from 350 to 500 °С the crystallite size of nickel has grown from 50 to 55 nm. Mean crystallite size of nickel oxide depended on temperature and ammonia content. In the temperature range from 350 to 500 °С the crystallite size of NiO has grown from 5 to 25 nm. Increasing ammonia content from 3.6 to 14.4 mol/mol Ni led to decreasing NiO crystallite size from 8-10 to 5 nm.  Keywords: Nickel ammine complexes, Nanopowders, IR-spectroscopy, XRD analysis, TG, DTA, DTG, Au-ger analysis, Slit pore structure, Free and fixed carbon concentrations.   PACS numbers: 81.07.Bc, 81.16.Be                                                             * i_risha@online.ua 1. INTRODUCTION  Nickel powders are widely used as electrode mate-rials in multilayered ceramic capacitors. Tendency of ceramic and electrode layers thinning to 100-200 nm that is used for increasing of capacitor dielectric capaci-ty leads to necessity of powders size decreasing to 10-20 nm. In addition powders those are used for capacitor electrode production should contain minimal impurity concentration because of high demands for electrical properties of capacitor. For example Na, K presence decreases powder electroconductivity and breakdown voltage of capacitor. Sulfur concentration in powder over 20 ppm leads to sizeable viscosity rising of elec-trode pastes for screen printing that complicates pro-cess of capacitors manufacturing. Carbon impairs pow-der conductivity and leads to increasing of Schottky barrier because of eutectic melting of electrode layers under sintering temperature as result of Ba/Ti/Ni al-loys formation. Complete or partial exchanging of Ni powder in green electrode layer on NiO can result in thinning of electrode during annealing in reductive atmosphere due to powder volume decreasing. In addition this ex-changing can decrease BaTiO3 concentration in elec-trode which is added with aim of balancing of sintering speeds of electrode and dielectric layers in the one hand and reduces the dielectric capacity of multilayered ce-ramic capacitor in the other hand. Thus, development of technology of Ni/NiO na-nopowders obtaining with particle size of 20 nm and less and minimal impurities content is of great im-portance.  2. MATERIALS AND METODS  Ni/NiO nanopowders with different metal and oxide phase ratio have been prepared by using thermal de-composition of nickel acetate ammine complexes which contain various ammonia concentrations at the tem-perature range 300-500 ºC in air. Chemical, phase composition and decomposition completeness of the products have been identified by IR-spectroscopy, XRD, chemical analysis and TG, DTA and DTG, respectively. Mean crystallite and particle size have been identified by TEM, SEM and laser granulometry. Pore size distribution of obtained pow-ders has been measured by the adsorption-structural method. Elements distribution according to particle depth has been identified by layer-by-layer Auger anal-ysis.  3. RESULTS AND DISCATION  3.1 Annealing Temperature Effect on Powder Composition and Particle Size  In accordance with TG (Fig. 1) and chemical (Fig. 2) analyses degree of initial complex decomposition de-pended on annealing temperature. Almost complete decomposition of nickel acetate hexaammine was ob-served at temperature range 375-500 °C. At lesser temperatures duration of annealing was insufficient for  I.O. DULINA, T.F. LOBUNETS, ET AL. PROC. NAP 3, 02NNPT02 (2014)   02NNPT02-2 full decomposition and powders consisted sizeable con-centration of nickel ammonia, aqua, hydroxide and carbonate complexes. Start of nickel and nickel oxide phases formation was observed at 325 °C as consistent with IR-spectroscopy and XRD data. But chemical phase analysis of obtained powders showed that per se NiO phase was formed at temperatures 400-450 °C only (Fig. 3). In our opinion this fact can be explained with presence of some amount of coordinated ammonia in oxide phase because of incomplete complex decompo-sition at annealing temperature 325-375 °C. At 500 °C process of ammonia removal was inhibited by rapid crystals grow in powder. This assumption was full co-ordinated with concentrations of free and fixed carbon in powders (Fig. 4). At temperature range 350-400 °C the minimal concentrations of free and fixed carbon were observed and this temperature range was the optimal for obtaining Ni/NiO powders with low carbon content.    Fig. 1 – Mass loss vs. decomposition temperature for nickel acetate hexaammine decomposition products  35455565758595300 350 400 450 500Decomposition temperature, °СNi total content, wt.%  Fig. 2 – Nickel total content vs. decomposition temperature for nickel acetate hexaammine decomposition products  In accordance with analysis of powder microstruc-ture the products with maximal area and volume of meso pores were observed at range 350-400 °C. For-mation of slit pore structure with mean pore size 3-4 nm led to the most complete complex decomposition and carbon removal from powder at this temperature range. In accordance with SEM microphotographs of pow-ders obtained at 325-500 °C were characterized with presence of agglomerates with wide particle size from 50 to 700-800 nm for all powder. But in whole increas-ing of annealing temperature resulted in agglomerates size rising. For powder obtained at 300 °C formation of nanocrystallites was not observed due to insufficient annealing temperature. TEM microphotographs of powders showed that agglomerates mainly consisted crystallites of Ni and NiO phases. For powders ob-tained at 350 and 400 °C some amount of Ni(OH)2 was observed which likely corresponded with ammonia-hydroxide precursors. Worth special mention that for-mation of crystalline phases of carbonate-containing precursors was not observed for XRD analysis and elec-tron-diffraction patterns of TEM. This can be explained with formation of crystalline hydroxide containing and amorphous carbonate containing precursors during thermal decomposition of nickel acetate ammines. Lay-er-by-layer Auger analysis of elements distribution ac-cording to agglomerate depth showed that the outer sur-face of agglomerate consist of carbon layer with depth 1-2 nm and NiO crystallites monolayer with depth 4-8 nm. The main body of agglomerate consisted of uniformly distributed crystallites of nickel and nickel oxide.  020406080300 350 400 450 500Decomposition temperature, ºСComponent content, wt. %Ni NiO Precursors  Fig. 3 – Chemical phase analysis vs. decomposition tempera-ture for nickel acetate hexaammine decomposition products  024681012300 350 400 450 500Decomposition temperature, ºСComponent content, wt. %С free С fixed   Fig. 4 – Carbon content analysis vs. decomposition tempera-ture for nickel acetate hexaammine decomposition products  Mean crystallite size of nickel and nickel oxide de-pended on temperature. In the temperature range from 350 to 500 °С the crystallite size of nickel had grown from 40-60 to 40-70 nm and nickel oxide from 5 to 20 – 25 nm. Particle size of 5 nm for nickel hydroxide am-mine remained unchanged with temperature. In accordance with results of experiments tempera-tures 350 and 400 °C were considered the more promis-ing for investigation of the process of thermal decompo-sition of nickel acetate ammines with aim Ni/NiO na-nopowders obtaining.  3.2 Annealing Duration Effect on Powder Com-position and Particle Size  In accordance with TG (Fig. 5) and chemical (Fig. 6) analyses almost complete decomposition of nickel ace-tate hexaammine was observed at 30 min of annealing at 400 °C and 60 min at 350 °C. Chemical phase analy-sis of obtained powders (Fig. 7) showed that at anneal-ing duration less than 30 min and over than 45 min at  FEATURES OF NI / NIO NANOPOWDER SYNTHESIS… PROC. NAP 3, 02NNPT02 (2014)   02NNPT02-3 400 °C per se NiO phase was not formed. In our opinion this fact was generated because of incomplete complex decomposition at lesser annealing duration and for-mation of secondary precursor phases which consisted of NiO with coordinated ammonia after 60-80 min of de-composition. But at annealing temperature 350 °C in-creasing of decomposition duration led to full precursor decomposition with forming Ni and NiO phases and sec-ondary precursors formation was not observed. Exchang-ing of nickel phase content in powders with increasing of decomposition time showed that decomposition process occurred in three stages: 1) Ni primary forming metal from precursors, 2) decomposing of residual nickel-containing precursors to NiO and 3) after reducing of NiO to Ni by ammonia and organic residuals. Exchanging of concentrations of free and fixed car-bon (Fig. 8) in powders depended on annealing temper-ature. At 400 °C increasing of annealing duration led to decreasing free and fixed carbon content in powders. But at 350 °C increase of decomposition time over 60 min resulted in some rising of free carbon concen-tration. The minimal free and fixed carbon concentra-tions were observed for powder obtained by decomposi-tion during 60 min at 350 °C. Analysis of powders microstructure showed that at annealing temperature 400 °C increasing of annealing duration led to pores size growth which corresponded with powder agglomerates size growth. According to SEM, TEM and laser granulometry at annealing dura-tion 20-25 min decreasing of agglomerates size was observed. Phase chemical analysis and IR-spectroscopy showed that this time range of annealing was corre-sponded to first and second decomposition stages. An-nealing duration increasing led to pore and agglomer-ates size growth because of third decomposition stage start. However at annealing temperature 350 °C in-creasing of annealing duration led to area and volume rising of pore with size 3-4 nm. This process was ac-companied with decreasing of powders agglomerates size. This fact showed that agglomerates size growth at third decomposition stage can be observed at sufficient annealing temperature only. Temperature 350 °C was an optimal one for obtaining Ni/NiO nanopowders with minimal agglomerate size.   Fig. 5 – Mass loss vs. decomposition duration for nickel ace-tate hexaammine decomposition products  5254565850 30 60 90 120 150 180Decomposition time, minNi total content, wt.%400 °C350 °C  Fig. 6 – Nickel total content vs. decomposition duration for nickel acetate hexaammine decomposition products 400 ºС0204060801000 30 60 90 120 150 180Decomposition time, minComponent content, wt. %Ni NiO Precursors350 ºС0204060801000 30 60 90 120 150 180Decomposition time, minComponent content, wt. %Ni NiO Precursors Fig. 7 – Chemical phase analysis vs. decomposition temperature for nickel acetate hexaammine decomposition products 400 ºС01234560 30 60 90 120 150 180Decomposition time, min Component content, wt. %С free С fixed350 ºС0246810120 30 60 90 120 150 180Decomposition time, minComponent content, wt. %С free С fixed  Fig. 8 – Carbon content analysis vs. decomposition temperature for nickel acetate hexaammine decomposition products  I.O. DULINA, T.F. LOBUNETS, ET AL. PROC. NAP 3, 02NNPT02 (2014)   02NNPT02-4 In accordance with results of experiments annealing times 60 and 30 min at 350 and 400 °C correspondently were considered the more promising for investigation of ammonia content effect on the process of thermal decomposition of nickel acetate ammines.  3.3 Ammonia Content Effect on Powder Compo-sition and Particle Size  TG and chemical analyses (Fig. 9) of powders ob-tained at 30 min of annealing at 400 °C and 60 min at 350 °C from nickel acetate ammines with different ammonia content in initial complex showed that pow-der decomposition degree depended on ammonia con-centration for annealing at 400 °C only. Almost com-plete decomposition of nickel acetate complexes was observed for complex ammonia content 6.5-9 mol/mol Ni2+ at 30 min of annealing at 400 °C and 6.5-8 mol/mol Ni2+ at 60 min and 350 °C. Analysis of powders microstructure showed that NH3 content changing in initial complex effected on pore size distribution. Decomposition process of com-plexes resulted in pore formation with mean size 3.3 and 3.7 nm. Rising of NH3 concentration in initial com-plex resulted in decreasing pore volume with size 3.3 nm and increasing with 3.7 nm. This fact showed that decomposition of ammonia-hydroxide and ammo-nia-carbonate precursors occurred with formation of different pore size 3.7 and 3.3 nm correspondently. 65707580853 6 9 12 15Ammonia content, mol NH3/mol Ni2+Ni total content, wt.%400 °С, 30 min 350 °С, 60 min  Fig. 9 – Nickel total content vs. ammonia content in initial complex for nickel acetate ammines decomposition products  SEM, TEM and laser granulometry analyses showed that rising of NH3 concentration in initial com-plex led to decreasing agglomerate sizes in powders. Mean crystallite size of nickel crystallites was un-changed with ammonia content. However increasing ammonia concentration from 3.6 to 14.4 mol/mol Ni2+ resulted in decreasing NiO crystallite size from 8-10 to 5 nm at 30 min annealing at 400 °C. In accordance with results of experiments ammonia concentration in initial complex of 6.5-9 and 6.5-8 mol/mol Ni2+ were considered the more optimal ones for Ni/NiO nanopowders obtaining by thermal decom-position of nickel acetate ammines at annealing times 60 and 30 min at 350 and 400 °C correspondently.  4. CONCLUSIONS  1. Thermal decomposition of nickel ammine com-plexes occurred with formation of crystalline hydrox-ide-containing and amorphous carbonate-containing precursors. Decomposition of ammonia-hydroxide and ammonia-carbonate precursors occurred with for-mation of different pore size 3.7 and 3.3 nm corre-spondently. 2. Decomposition process occurred in three stages: 1) Ni primary forming from nickel ammine-hydroxide complexes, 2) decomposing of residual nickel-containing precursors to NiO and 3) after reducing of NiO to Ni by ammonia and organic residuals. These stages were accompanied with exchanging of powders pore structure and agglomerate sizes. 3. The most optimal condition for Ni/NiO nanopow-ders obtaining by thermal decomposition of nickel ace-tate ammines were considered ammonia concentration in initial complex of 6.5-9 and 6.5-8 mol/mol Ni2+ at annealing times 60 and 30 min at 350 and 400 °C cor-respondently. 4. The minimal free and fixed carbon concentrations were observed for powder obtained by decomposition during 60 min at 350 °C. 5. Mean crystallite size of nickel depended on tem-perature only. In the temperature range from 350 to 500 °С the crystallite size of nickel has grown from 50 to 55 nm. 6. Mean crystallite size of nickel oxide depended on temperature and ammonia content. In the temperature range from 350 to 500 °С the crystallite size of NiO has grown from 5 to 25 nm. Increasing of ammonia content from 3.6 to 14.4 mol/mol Ni led to decreasing NiO crys-tallite size from 8-10 to 5 nm.  AKNOWLEDGEMENTS  Authors are grateful to V. Tkach from Bakul Institute for Superhard Materials of NASU, N. Danylenko from Frantsevich Institute for Problems of Materials Science of NASU and Yu. Romanenko from National Technical Uni-versity of Ukraine “Kyiv Polytechnical Institute” for mi-croscopic investigations and the State Agency on Science, Innovations and Informatization of Ukraine for a financial support for the project NN352-2013.  

Features of Ni / NiO Nanopowder Synthesis by Thermal Decomposition of Nickel Acetate  Amines: Effect of Annealing Temperature and Duration and Ammonia Content on Powder  Composition and Particle Size

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 3 No 2, 02NNPT02(4pp) (2014) 
 
 
2304-1862/2014/3(2)02NNPT02(4) 02NNPT02-1  2014 Sumy State University 
Features of Ni / NiO Nanopowder Synthesis by Thermal Decomposition of Nickel Acetate 
Amines: Effect of Annealing Temperature and Duration and Ammonia Content on Powder 
Composition and Particle Size 
 
I.O. Dulina*, T.F. Lobunets, L.O. Klochkov, A.V. Ragulya 
 
Frantsevich Institute for Problems of Materials Science of NASU, 3, Krzhyzhanovsky Str., 
03142 Kyiv, Ukraine 
 
(Received 02 May 2014; published online 29 August 2014) 
 
Ni/NiO nanopowders with different metal and oxide phase ratio have been prepared by using thermal 
decomposition of nickel acetate ammine complexes which contain various ammonia concentrations at the 
temperature range 300-500 ºC in air. Obtained powders have been characterized by IR-spectroscopy, XRD 
and TG, DTA, DTG, TEM, laser granulometry, adsorption-structural method and layer-by-layer Auger 
analysis. Thermal decomposition of nickel ammine complexes occurred with formation of crystalline hy-
droxide containing and amorphous carbonate containing precursors. Changing of precursors composition 
with different NH3 content and annealing duration and temperature leads to different pore structure, ag-
glomerate size of powders and determinates free and fixed carbon concentrations. Mean crystallite size of 
nickel depended on temperature only. In the temperature range from 350 to 500 °С the crystallite size of 
nickel has grown from 50 to 55 nm. Mean crystallite size of nickel oxide depended on temperature and 
ammonia content. In the temperature range from 350 to 500 °С the crystallite size of NiO has grown from 
5 to 25 nm. Increasing ammonia content from 3.6 to 14.4 mol/mol Ni led to decreasing NiO crystallite size 
from 8-10 to 5 nm. 
 
Keywords: Nickel ammine complexes, Nanopowders, IR-spectroscopy, XRD analysis, TG, DTA, DTG, Au-
ger analysis, Slit pore structure, Free and fixed carbon concentrations. 
 
 PACS numbers: 81.07.Bc, 81.16.Be 
 
 
                                                          
* i_risha@online.ua 
1. INTRODUCTION 
 
Nickel powders are widely used as electrode mate-
rials in multilayered ceramic capacitors. Tendency of 
ceramic and electrode layers thinning to 100-200 nm 
that is used for increasing of capacitor dielectric capaci-
ty leads to necessity of powders size decreasing to 10-
20 nm. In addition powders those are used for capacitor 
electrode production should contain minimal impurity 
concentration because of high demands for electrical 
properties of capacitor. For example Na, K presence 
decreases powder electroconductivity and breakdown 
voltage of capacitor. Sulfur concentration in powder 
over 20 ppm leads to sizeable viscosity rising of elec-
trode pastes for screen printing that complicates pro-
cess of capacitors manufacturing. Carbon impairs pow-
der conductivity and leads to increasing of Schottky 
barrier because of eutectic melting of electrode layers 
under sintering temperature as result of Ba/Ti/Ni al-
loys formation. 
Complete or partial exchanging of Ni powder in 
green electrode layer on NiO can result in thinning of 
electrode during annealing in reductive atmosphere 
due to powder volume decreasing. In addition this ex-
changing can decrease BaTiO3 concentration in elec-
trode which is added with aim of balancing of sintering 
speeds of electrode and dielectric layers in the one hand 
and reduces the dielectric capacity of multilayered ce-
ramic capacitor in the other hand. 
Thus, development of technology of Ni/NiO na-
nopowders obtaining with particle size of 20 nm and 
less and minimal impurities content is of great im-
portance. 
 
2. MATERIALS AND METODS 
 
Ni/NiO nanopowders with different metal and oxide 
phase ratio have been prepared by using thermal de-
composition of nickel acetate ammine complexes which 
contain various ammonia concentrations at the tem-
perature range 300-500 ºC in air. 
Chemical, phase composition and decomposition 
completeness of the products have been identified by 
IR-spectroscopy, XRD, chemical analysis and TG, DTA 
and DTG, respectively. Mean crystallite and particle 
size have been identified by TEM, SEM and laser 
granulometry. Pore size distribution of obtained pow-
ders has been measured by the adsorption-structural 
method. Elements distribution according to particle 
depth has been identified by layer-by-layer Auger anal-
ysis. 
 
3. RESULTS AND DISCATION 
 
3.1 Annealing Temperature Effect on Powder 
Composition and Particle Size 
 
In accordance with TG (Fig. 1) and chemical (Fig. 2) 
analyses degree of initial complex decomposition de-
pended on annealing temperature. Almost complete 
decomposition of nickel acetate hexaammine was ob-
served at temperature range 375-500 °C. At lesser 
temperatures duration of annealing was insufficient for 
 I.O. DULINA, T.F. LOBUNETS, ET AL. PROC. NAP 3, 02NNPT02 (2014) 
 
 
02NNPT02-2 
full decomposition and powders consisted sizeable con-
centration of nickel ammonia, aqua, hydroxide and 
carbonate complexes. Start of nickel and nickel oxide 
phases formation was observed at 325 °C as consistent 
with IR-spectroscopy and XRD data. But chemical 
phase analysis of obtained powders showed that per se 
NiO phase was formed at temperatures 400-450 °C 
only (Fig. 3). In our opinion this fact can be explained 
with presence of some amount of coordinated ammonia 
in oxide phase because of incomplete complex decompo-
sition at annealing temperature 325-375 °C. At 500 °C 
process of ammonia removal was inhibited by rapid 
crystals grow in powder. This assumption was full co-
ordinated with concentrations of free and fixed carbon 
in powders (Fig. 4). At temperature range 350-400 °C 
the minimal concentrations of free and fixed carbon 
were observed and this temperature range was the 
optimal for obtaining Ni/NiO powders with low carbon 
content. 
 
 
 
Fig. 1 – Mass loss vs. decomposition temperature for nickel 
acetate hexaammine decomposition products 
 
35
45
55
65
75
85
95
300 350 400 450 500
Decomposition temperature, °С
N
i 
to
ta
l 
c
o
n
te
n
t,
 w
t.
%
 
 
Fig. 2 – Nickel total content vs. decomposition temperature 
for nickel acetate hexaammine decomposition products 
 
In accordance with analysis of powder microstruc-
ture the products with maximal area and volume of 
meso pores were observed at range 350-400 °C. For-
mation of slit pore structure with mean pore size 3-
4 nm led to the most complete complex decomposition 
and carbon removal from powder at this temperature 
range. 
In accordance with SEM microphotographs of pow-
ders obtained at 325-500 °C were characterized with 
presence of agglomerates with wide particle size from 
50 to 700-800 nm for all powder. But in whole increas-
ing of annealing temperature resulted in agglomerates 
size rising. For powder obtained at 300 °C formation of 
nanocrystallites was not observed due to insufficient 
annealing temperature. TEM microphotographs of 
powders showed that agglomerates mainly consisted 
crystallites of Ni and NiO phases. For powders ob-
tained at 350 and 400 °C some amount of Ni(OH)2 was 
observed which likely corresponded with ammonia-
hydroxide precursors. Worth special mention that for-
mation of crystalline phases of carbonate-containing 
precursors was not observed for XRD analysis and elec-
tron-diffraction patterns of TEM. This can be explained 
with formation of crystalline hydroxide containing and 
amorphous carbonate containing precursors during 
thermal decomposition of nickel acetate ammines. Lay-
er-by-layer Auger analysis of elements distribution ac-
cording to agglomerate depth showed that the outer sur-
face of agglomerate consist of carbon layer with depth 1-
2 nm and NiO crystallites monolayer with depth 4-8 nm. 
The main body of agglomerate consisted of uniformly 
distributed crystallites of nickel and nickel oxide. 
 
0
20
40
60
80
300 350 400 450 500
Decomposition temperature, ºС
C
o
m
p
o
n
e
n
t 
c
o
n
te
n
t,
 w
t.
 %
Ni NiO Precursors
 
 
Fig. 3 – Chemical phase analysis vs. decomposition tempera-
ture for nickel acetate hexaammine decomposition products 
 
0
2
4
6
8
10
12
300 350 400 450 500
Decomposition temperature, ºС
C
o
m
p
o
n
e
n
t 
c
o
n
te
n
t,
 w
t.
 %
С free С fixed  
 
Fig. 4 – Carbon content analysis vs. decomposition tempera-
ture for nickel acetate hexaammine decomposition products 
 
Mean crystallite size of nickel and nickel oxide de-
pended on temperature. In the temperature range from 
350 to 500 °С the crystallite size of nickel had grown 
from 40-60 to 40-70 nm and nickel oxide from 5 to 20 – 
25 nm. Particle size of 5 nm for nickel hydroxide am-
mine remained unchanged with temperature. 
In accordance with results of experiments tempera-
tures 350 and 400 °C were considered the more promis-
ing for investigation of the process of thermal decompo-
sition of nickel acetate ammines with aim Ni/NiO na-
nopowders obtaining. 
 
3.2 Annealing Duration Effect on Powder Com-
position and Particle Size 
 
In accordance with TG (Fig. 5) and chemical (Fig. 6) 
analyses almost complete decomposition of nickel ace-
tate hexaammine was observed at 30 min of annealing 
at 400 °C and 60 min at 350 °C. Chemical phase analy-
sis of obtained powders (Fig. 7) showed that at anneal-
ing duration less than 30 min and over than 45 min at 
 FEATURES OF NI / NIO NANOPOWDER SYNTHESIS… PROC. NAP 3, 02NNPT02 (2014) 
 
 
02NNPT02-3 
400 °C per se NiO phase was not formed. In our opinion 
this fact was generated because of incomplete complex 
decomposition at lesser annealing duration and for-
mation of secondary precursor phases which consisted of 
NiO with coordinated ammonia after 60-80 min of de-
composition. But at annealing temperature 350 °C in-
creasing of decomposition duration led to full precursor 
decomposition with forming Ni and NiO phases and sec-
ondary precursors formation was not observed. Exchang-
ing of nickel phase content in powders with increasing of 
decomposition time showed that decomposition process 
occurred in three stages: 1) Ni primary forming metal 
from precursors, 2) decomposing of residual nickel-
containing precursors to NiO and 3) after reducing of 
NiO to Ni by ammonia and organic residuals. 
Exchanging of concentrations of free and fixed car-
bon (Fig. 8) in powders depended on annealing temper-
ature. At 400 °C increasing of annealing duration led to 
decreasing free and fixed carbon content in powders. 
But at 350 °C increase of decomposition time over 
60 min resulted in some rising of free carbon concen-
tration. The minimal free and fixed carbon concentra-
tions were observed for powder obtained by decomposi-
tion during 60 min at 350 °C. 
Analysis of powders microstructure showed that at 
annealing temperature 400 °C increasing of annealing 
duration led to pores size growth which corresponded 
with powder agglomerates size growth. According to 
SEM, TEM and laser granulometry at annealing dura-
tion 20-25 min decreasing of agglomerates size was 
observed. Phase chemical analysis and IR-spectroscopy 
showed that this time range of annealing was corre-
sponded to first and second decomposition stages. An-
nealing duration increasing led to pore and agglomer-
ates size growth because of third decomposition stage 
start. However at annealing temperature 350 °C in-
creasing of annealing duration led to area and volume 
rising of pore with size 3-4 nm. This process was ac-
companied with decreasing of powders agglomerates 
size. This fact showed that agglomerates size growth at 
third decomposition stage can be observed at sufficient 
annealing temperature only. Temperature 350 °C was 
an optimal one for obtaining Ni/NiO nanopowders with 
minimal agglomerate size. 
 
 
Fig. 5 – Mass loss vs. decomposition duration for nickel ace-
tate hexaammine decomposition products 
 
5
25
45
65
85
0 30 60 90 120 150 180
Decomposition time, min
N
i 
to
ta
l 
c
o
n
te
n
t,
 w
t.
%
400 °C
350 °C
 
 
Fig. 6 – Nickel total content vs. decomposition duration for 
nickel acetate hexaammine decomposition products 
400 ºС
0
20
40
60
80
100
0 30 60 90 120 150 180
Decomposition time, min
C
o
m
p
o
n
e
n
t 
c
o
n
te
n
t,
 w
t.
 %
Ni NiO Precursors
350 ºС
0
20
40
60
80
100
0 30 60 90 120 150 180
Decomposition time, min
C
o
m
p
o
n
e
n
t 
c
o
n
te
n
t,
 w
t.
 %
Ni NiO Precursors
 
Fig. 7 – Chemical phase analysis vs. decomposition temperature for nickel acetate hexaammine decomposition products 
400 ºС
0
1
2
3
4
5
6
0 30 60 90 120 150 180
Decomposition time, min 
C
o
m
p
o
n
e
n
t 
c
o
n
te
n
t,
 w
t.
 %
С free С fixed
350 ºС
0
2
4
6
8
10
12
0 30 60 90 120 150 180
Decomposition time, min
C
o
m
p
o
n
e
n
t 
c
o
n
te
n
t,
 w
t.
 %
С free С fixed
 
 
Fig. 8 – Carbon content analysis vs. decomposition temperature for nickel acetate hexaammine decomposition products 
 I.O. DULINA, T.F. LOBUNETS, ET AL. PROC. NAP 3, 02NNPT02 (2014) 
 
 
02NNPT02-4 
In accordance with results of experiments 
annealing times 60 and 30 min at 350 and 400 °C 
correspondently were considered the more promising 
for investigation of ammonia content effect on the 
process of thermal decomposition of nickel acetate 
ammines. 
 
3.3 Ammonia Content Effect on Powder Compo-
sition and Particle Size 
 
TG and chemical analyses (Fig. 9) of powders ob-
tained at 30 min of annealing at 400 °C and 60 min at 
350 °C from nickel acetate ammines with different 
ammonia content in initial complex showed that pow-
der decomposition degree depended on ammonia con-
centration for annealing at 400 °C only. Almost com-
plete decomposition of nickel acetate complexes was 
observed for complex ammonia content 6.5-9 mol/mol 
Ni2+ at 30 min of annealing at 400 °C and 6.5-8 mol/mol 
Ni2+ at 60 min and 350 °C. 
Analysis of powders microstructure showed that 
NH3 content changing in initial complex effected on 
pore size distribution. Decomposition process of com-
plexes resulted in pore formation with mean size 3.3 
and 3.7 nm. Rising of NH3 concentration in initial com-
plex resulted in decreasing pore volume with size 
3.3 nm and increasing with 3.7 nm. This fact showed 
that decomposition of ammonia-hydroxide and ammo-
nia-carbonate precursors occurred with formation of 
different pore size 3.7 and 3.3 nm correspondently. 
65
70
75
80
85
3 6 9 12 15
Ammonia content, mol NH3/mol Ni
2+
N
i 
to
ta
l 
c
o
n
te
n
t,
 w
t.
%
400 °С, 30 min 350 °С, 60 min
 
 
Fig. 9 – Nickel total content vs. ammonia content in initial 
complex for nickel acetate ammines decomposition products 
 
SEM, TEM and laser granulometry analyses 
showed that rising of NH3 concentration in initial com-
plex led to decreasing agglomerate sizes in powders. 
Mean crystallite size of nickel crystallites was un-
changed with ammonia content. However increasing 
ammonia concentration from 3.6 to 14.4 mol/mol Ni2+ 
resulted in decreasing NiO crystallite size from 8-10 to 
5 nm at 30 min annealing at 400 °C. 
In accordance with results of experiments ammonia 
concentration in initial complex of 6.5-9 and 6.5-
8 mol/mol Ni2+ were considered the more optimal ones 
for Ni/NiO nanopowders obtaining by thermal decom-
position of nickel acetate ammines at annealing times 
60 and 30 min at 350 and 400 °C correspondently. 
 
4. CONCLUSIONS 
 
1. Thermal decomposition of nickel ammine com-
plexes occurred with formation of crystalline hydrox-
ide-containing and amorphous carbonate-containing 
precursors. Decomposition of ammonia-hydroxide and 
ammonia-carbonate precursors occurred with for-
mation of different pore size 3.7 and 3.3 nm corre-
spondently. 
2. Decomposition process occurred in three stages: 
1) Ni primary forming from nickel ammine-hydroxide 
complexes, 2) decomposing of residual nickel-
containing precursors to NiO and 3) after reducing of 
NiO to Ni by ammonia and organic residuals. These 
stages were accompanied with exchanging of powders 
pore structure and agglomerate sizes. 
3. The most optimal condition for Ni/NiO nanopow-
ders obtaining by thermal decomposition of nickel ace-
tate ammines were considered ammonia concentration 
in initial complex of 6.5-9 and 6.5-8 mol/mol Ni2+ at 
annealing times 60 and 30 min at 350 and 400 °C cor-
respondently. 
4. The minimal free and fixed carbon concentrations 
were observed for powder obtained by decomposition 
during 60 min at 350 °C. 
5. Mean crystallite size of nickel depended on tem-
perature only. In the temperature range from 350 to 
500 °С the crystallite size of nickel has grown from 50 
to 55 nm. 
6. Mean crystallite size of nickel oxide depended on 
temperature and ammonia content. In the temperature 
range from 350 to 500 °С the crystallite size of NiO has 
grown from 5 to 25 nm. Increasing of ammonia content 
from 3.6 to 14.4 mol/mol Ni led to decreasing NiO crys-
tallite size from 8-10 to 5 nm. 
 
AKNOWLEDGEMENTS 
 
Authors are grateful to V. Tkach from Bakul Institute 
for Superhard Materials of NASU, N. Danylenko from 
Frantsevich Institute for Problems of Materials Science of 
NASU and Yu. Romanenko from National Technical Uni-
versity of Ukraine “Kyiv Polytechnical Institute” for mi-
croscopic investigations and the State Agency on Science, 
Innovations and Informatization of Ukraine for a financial 
support for the project NN352-2013. 
 


English

https://essuir.sumdu.edu.ua/bitstream/123456789/37193/1/dulina_nanopowders.pdf

Features of Ni / NiO Nanopowder Synthesis by Thermal Decomposition of Nickel Acetate Amines: Effect of Annealing Temperature and Duration and Ammonia Content on Powder Composition and Particle Size

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