Growth of pure Ni(OH)2 single crystals from solution - Control of the crystal size

Article abstract of DOI:10.1002/1521-3749(200213)628:13<2818::AID-ZAAC2818>3.0.CO;2-J

A new synthesis route, based on the hydrolysis of Na₂[Ni(OH)₄] is presented which leads to pure single crystalline nickel hydroxide with crystal sizes up to 0.25 mm. The effect of varying preparation conditions on the crystal size is investigated.

Full text of DOI:10.1002/1521-3749(200213)628:13<2818::AID-ZAAC2818>3.0.CO;2-J

Growth of Pure Ni(OH) Single Crystals from Solution ؊ Control of the
2
Crystal Size
H. Wallner * and K. Gattererb
a
a
Leoben/Austria, Institut für Physikalische Chemie, Montanuniversität Leoben
b
Graz/Austria, Institut für Physikalische und Theoretische Chemie der Technischen Universität Graz
th
th
Received April 15 , 2002; revised July 24 , 2002.
Abstract. A new synthesis route, based on the hydrolysis of
varying preparation conditions on the crystal size is investigated.
2 4
Na [Ni(OH) ] is presented which leads to pure single crystalline
nickel hydroxide with crystal sizes up to 0.25 mm. The effect of
Keywords: Nickel; Nickel hydroxide
Natural nickel hydroxide (theophrastite) named after the Greek
philosopher Theophratos occurs as a gangue mineral in the mag-
netite-chromite ores in the Vermion region of northern Greece and
in Tasmania (Heazlewood) Australia [1, 2]. Although Williams et
al. reported the natural occurrence of nickel hydroxide and demon-
strated its authenticity by X-ray powder diffraction, they were un-
able to ascertain the chemistry [3]. Nickel hydroxide (thermo-
Experimental
Analytical grade reagents, bidistilled water free of carbon dioxide,
high purity Ni(ClO
52 g NaOH and 48 g H
NaOH pellets were melted an aqueous solution prepared of 10g
Ni(ClO O and 6g H O was added dropwise. A pale-green
amorphous precipitate formed rapidly and was transformed into
olive-green Na [Ni(OH) ] by keeping the solution at 140°C for 24
4
)
2·6H
2
O and NaOH were used throughout.
O were heated to 140°C. When all the
1
2
4
)
2·6 H
2
2
dynamic stable form β-Ni(OH)
2
) crystallises in the trigonal system
¯
2
4
with space group P3m1 which is common to several other M(OH)
2
hours [9]. This part of the synthesis was performed in a teflon flask
equipped with a reflux condenser and an electromagnetic stirrer.
The use of teflon was necessary because the mixture corrodes con-
ventional laboratory glass rapidly. When the reaction is finished
an olive-green coarse-crystalline precipitate can be located on the
bottom of the flask. The major part of the molten sodium hydrox-
hydroxides ( M ϭ Mg, Mn, Fe, Co, Cd, Ca)[4]. Its structure can
be described as a hexagonal close packing of hydroxyl ions (AB-
ABA-type) where the cations occupy the octahedral sites.
Theophrastite corresponds to the chemical formula Ni(OH)
2
but
the natural mineral cannot be investigated in the pure state for
it is variably intermixed with diverse hydroxides and possibly an
2
ide is removed and well crystallized Ni(OH) with crystal sizes of
amorphous nickel sulphate. The common way to obtain Ni(OH)
synthetically is through precipitation of aqueous NiCl , Ni(NO
or NiSO
There are also methods using ammonia, sodium carbonate and
strong organic bases to synthesise Ni(OH) [6].
2
about 0.1 mm is obtained by boiling the reaction product in water
for 24 hours. The mother liquor was sucked off and the precipitate
washed free of sodium hydroxide with water. After removing most
of the water with ethyl alcohol, the crystals were dried in a hot air
cabinet at 100°C. At higher temperatures (above 200°C) the well
crystallised theophrastite decomposed to nickel oxide.
It was found that by modifying the procedure described above a
variation of the maximal final size of the crystallites can be
achieved (see Table 1). Larger crystallites up to about 0.25 mm
diameter can be grown by raising the temperature to 170°C and
2
3 2
)
4
solutions with NaOH or KOH solutions in excess [5].
2
All these routes result in tiny, partially amorphous particles as well
as materials consisting of various nickel hydroxy-salt phases. The
remarkable low tendency of nickel hydroxide to form larger well
characterised crystallites is illustrated in a work of Lin et al. [7].
Their work is based on the studies of Feitknecht [8] and compares
aged and fresh precipitates for which different solubility constants
are reported.
4 2
by using only 6 g Ni(ClO )2·6 H O instead of 10 g. The higher
temperatures however cause partial formation of nickel ions of
In the present work we report
a
synthesis route for
β- Ni(OH) which leads to a well characterised and pure material
with crystallites up to 0.25 mm diameter, without foreign anion
inclusions. The method employs the hydrolysis reaction of
2
Table 1 Experimental conditions for preparations P1 to P6 (i.e.,
concentration of NaOH solution, content of Ni solution, and
temperature at which the amorphous precipitate was kept for 24
hours), and maximal crystal sizes (diameter) of β-Ni(OH) ob-
2
tained.
2
ϩ
2 4
Na [Ni(OH) ] which was obtained by a method proposed by
Scholder and Giesler [9].
Ni2 content
moles in 200g
NaOH solution
ϩ
T
°C
Max. crystal size
mm
Preparation NaOH
conc. %
*
Harald Wallner
Institut für Physikalische Chemie
Montanuniversität Leoben
Franz-Josef-Str.18
A-87000 Leoben
Fax: 0043/3842/402 335
P1
P2
P3
P4
P5
P6
63
76
76
76
76
76
0.0328
0.0328
0.0273
0.0328
0.0273
0.0164
110
140
140
160
170
170
micro-crystalline
0.025
0.050
0.060
0.100
0.250
E-mail: Harald.Wallner@unileoben.ac.at
2818
 2002 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 0044Ϫ2313/02/628/2818Ϫ2820 $ 20.00ϩ.50/0 Z. Anorg. Allg. Chem. 2002, 628, 2818Ϫ2820

2
Growth of Pure Ni(OH) Single Crystals from Solution
Figure 2 IR transmittance spectra of theophrastite samples pre-
pared according to P5 (solid), and P1(dotted) in comparison with
2
the corresponding spectra of Ni(OH) samples prepared by conven-
tional ways, CP1 ( dashed and dotted) and CP2 (dashed).
Figure 1 Sanning electron microscope photograph of crystalline
theophrastite obtained with preparation P5 (for experimental
conditions see Table).The length of the white bar is 10 µm.
texture phenomena. These texture peaks are caused by the layered
structure of the theophrastite crystals.
higher oxidation states and the precipitate becomes almost black.
Smaller crystallites (micro-crystalline material up to 0.1 mm crys-
The IR spectra of two theophrastite samples P5 and P1 are com-
pared in Fig. 2 with the spectra of samples CP1 and CP2. The
spectra are dominated by the strong stretching vibration of the OH
2
ϩ
tals) are obtained by changing the ratio of hydroxide to Ni , where
an increase of the nickel content leads to smaller Ni(OH) crystals
sizes. Micro-crystalline material can be obtained by using 200 g
2
Ϫ1
group at 3640 cm . In the case of the P5 sample this band has a
Ϫ1
small half-width (FWHM) of only 20 cm . Towards lower energy
63% NaOH and 12 g Ni(ClO
4 2 2
) .6 H O by keeping the mixture at
Ϫ1
at 3580 cm the band has a prominent shoulder. The FWHM of
110°C for 24 hours. It is important for all experiments to add a
this band for the four samples depicted in Fig. 2 increases as
saturated solution of nickel perchlorate dropwise to the melted so-
dium hydroxide (the NaOH concentration should not be changed
too much by the precipitation). The various experimental con-
ditions (P1 to P6) together with the maximal crystal sizes achieved
are collected in the Table. The chemical analysis of Ni2 has been
carried out by titration with EDTA. The difference between
Ϫ1
Ϫ1
Ϫ1
Ϫ1
2
0 cm (P5), 45 cm (P1), 40 cm (CP1) and >300 cm (CP2).
The reduced transmittance in the spectral region from 3500 to 3000
Ϫ1
Ϫ1
cm and the band at 1600 cm are due to water. While the water
absorptions are present in all samples (and can hardly be avoided
when the preparation involves aqueous solutions) they are clearly
minimized in the case of the coarse crystalline product P5. The
ϩ
2
theoretical and titrated value referred to Ni(OH) averages 0.28 %.
Ni(OH)
2
sample obtained from the NH
3
solution (CP2), even after
absorptions in the region
Fig.1 shows a scanning electron microscope photograph of crystal-
line theophrastite obtained from preparation P5. For comparison
of IR spectra nickel hydroxide was also prepared by two conven-
tional methods. Method CP1 consists of preparing solutions with
purification, still shows prominent NH
3
Ϫ1
between 700 and 1500 cm
In the present work we have shown that pure theophrastite
β-Ni(OH) ) can be obtained by a preparation route employing
the hydrolysis reaction of Na [Ni(OH) ]. With this well charac-
.
(
2
3 2
25 g KOH and 60 g Ni(NO ) in 250 ml deionized water free of
2
4
carbon dioxide, respectively. The KOH solution was added drop-
wise under stirring to the second solution kept at 35°C [5]. In
terized single crystalline material the determination of reliable
thermodynamic properties like, e.g., solubility constants will be
possible. Results of these measurements will be reported else-
where [11].
method CP2 the Ni(NO
concentrated solution of NH
3
)
2
solution was added dropwise to a heated
. Included anions were removed from
3
the product by boiling the reaction mixture for several hours [10].
The precipitates in both cases were purified and treated in the same
way as the well crystallized theophrastite described above.
Acknowledgement. H.W. sincerely thanks Prof. H. Gamsjäger
Powder X-ray spectra of the samples were obtained using a Siemens
(Leoben) for initiating and constructively discussing this work.
5
000 X-ray diffractometer and Cu Kα radiation. IR transmittance
Ϫ1
spectra (4000 Ϫ 400 cm ) of the material were obtained with the
KBr technique using a Perkin Elmer 325 double-beam spec-
trometer with a blank KBr pill in the reference beam.
[
[
[
[
1] A. Livingstone, D. L. Bish, Mineral. Mag. 1982, 46, 1.
2] T. Marcopoulos, M. Economou, Am. Mineral. 1981, 66, 1020.
3] K. L. Williams, Am. Mineral. 1960, 45, 1109.
4] C. Mockenhaupt, Strukturuntersuchungen an Amminkom-
plexen und Hydroxiden von Übergangsmetallen. PhD Thesis
Universität-Gesamthochschule Siegen, Germany 1999.
Results and Discussion
The X-ray diffraction patterns of crystalline theophrastites pre-
pared according to P1 and P5 show only peaks expected for
Ni(OH)
2
and agree satisfactorily with those given in the JCPDS-
[5] G. Brauer, Handbuch der präperativen anorganischen Chemie, 2
ICDD card 14 117. There are some weaker features representing
nd. Ed., Vol.2, Stuttgart 1962, p.1347/8.
Z. Anorg. Allg. Chem. 2002, 628, 2818Ϫ2820
2819

H. Wallner, K. Gatterer
[
[
[
[
6] C. Cabannes-Ott, Ann. Chim. 1960, 5, 905.
[10] S. Okada, T. Shiraishi, K. Watanabe, Kongyo Kagaku Zasshi,
7] X. Lin, R. C. Burns, G. A. Lawrance, Wat. Res. 1998, 32, 3637.
8] W. Feitknecht, L. Hartmann, Helv. Chim. Acta 1954, 8, 95.
9] R. Scholder, E. Giesler, Z. Anorg. Allg. Chem. 1962, 316, 237.
1948, 51, 129.
[11] H. Gamsjäger, H. Wallner, W. Preis, Monatsh. Chem. 2002,
133, 225.
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Z. Anorg. Allg. Chem. 2002, 628, 2818Ϫ2820