Size controlled mechanochemical synthesis of ZrSi2

Article abstract of DOI:10.1039/c2cc36323b

Mechanochemical metathesis reactions were utilized to synthesize nanocrystalline ZrSi₂ ranging from 9-30 nm in size. Size was controlled through dilution with CaCl₂. A linear relationship was found between diluent concentration and crystallite size. Unlike typical self-propagating metathesis reactions, this reaction did not self-propagate, requiring the input of mechanical energy.

Full text of DOI:10.1039/c2cc36323b

View Article Online / Journal Homepage
ChemComm
Accepted Manuscript
This is an Accepted Manuscript, which has been through the RSC Publishing peer
review process and has been accepted for publication.
Accepted Manuscripts are published online shortly after acceptance, which is prior
to technical editing, formatting and proof reading. This free service from RSC
Publishing allows authors to make their results available to the community, in
citable form, before publication of the edited article. This Accepted Manuscript will
be replaced by the edited and formatted Advance Article as soon as this is available.
Chemical Communications
www.rsc.org/chemcomm
Volume 46
| Number 32 | 28 August 2010 | Pages 5813–5976
To cite this manuscript please use its permanent Digital Object Identifier (DOI®),
which is identical for all formats of publication.
More information about Accepted Manuscripts can be found in the
Information for Authors.
Please note that technical editing may introduce minor changes to the text and/or
graphics contained in the manuscript submitted by the author(s) which may alter
content, and that the standard Terms & Conditions and the ethical guidelines
that apply to the journal are still applicable. In no event shall the RSC be held
responsible for any errors or omissions in these Accepted Manuscript manuscripts or
any consequences arising from the use of any information contained in them.
ISSN 1359-7345
COMMUNICATION
FEATURE ARTICLE
J. Fraser Stoddart et al.
Directed self-assembly of
ring-in-ring complex
Wenbin Lin et al.
a
Hybrid nanomaterials for biomedical
applications
1359-7345(2010)46:32;1-H
www.rsc.org/chemcomm
Registered Charity Number 207890

ChemComm
Page 1 of 3Journal Name
Dynamic Article Links ►
View Article Online
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
Size Controlled Mechanochemical Synthesis of ZrSi2
David Restrepoa, Sandra M. Hick, a Carolin Griebel, a Juan Alarcon, a Kyle Giesler, a Yan Chen, b Nina
Orlovskaya, b Richard G. Blaira, c,
*
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
Mechanochemical metathesis reactions were utilized to
synthesize nanocrystalline ZrSi2 ranging from 9-30 nm in
size. Size was controlled through dilution with CaCl2.
10 linear relationship was found between diluent concentration
and crystallite size. Unlike typical self-propagating
A
metathesis reactions, this reaction did not self-propagate,
requiring the input of mechanical energy.
15
Transition metal silicides, which are refractory, conductive,
strong, and relatively inert, offer an attractive choice for
1,
2
reinforcement materials
.
In particular, nanocrystalline
refractory silicides are more desirable due to their novel
properties, such as high strength, hardness, and electrical
20 conductivity 2. Because of these properties and its low electrical
resisitivity (13 – 34 ꢀꢀ cm)3 zirconium silicide is used in
Figure 1. XRD patterns of the mechanochemically synthesized ZrSi2 at
50 different diluent loadings. By adding an inert diluent (CaCl2) the
crystallite size can be reduced. All patterns match ZrSi2 (JCꢁPDS 32ꢁ
1499).
4,
composites as a reinforcement material 5, in microelectronic
7
devices 6, and potentially in neutron deflectors
.
Recently,
nanoinclusions of conductive materials have been proposed as a
25 route to improved thermoelectric materials.8, 9 Incorporation of
gold nanoparticles in a Bi2Te3 matrix resulted in an improved
using mechanochemical synthesis via a metathesis reaction.
Although mechanochemical methods have been used to prepare a
Power Factor and Figure of Merit. This result shows that a top 55 variety of nanomaterials, 18ꢁ23 the synthesis of refractory materials
down approach to improving thermoelectric materials is practical.
However, gold is not compatible with thermoelectric materials
30 used at higher temperatures. In particular, the SiGe alloy
currently used in radioisotope thermoelectric generators (RTGs)
by mechanically driven solidꢁstate metathesis has not been
investigated thoroughly. This approach involves grinding the
starting materials in a highꢁenergy ball mill. By using a diluent,
crystallite size is controlled enabling the production of ZrSi2 with
is processed at temperatures above the melting point of gold and 60 sizes dependent on the level of dilution. Although, size control in
nanostructures would be lost. It has been proposed that
nanoparticles of silicides can enhance the thermoelectric
35 properties of SiGe.10 Current approaches to producing silicide
inclusions rely on a bottom up approach through the formation of
selfꢁpropagating metathesis reaction has been investigated in the
past,24 the extent of control was limited by the need for selfꢁ
propagation. A mechanochemical approach eliminates this
restriction, since selfꢁpropagation is not necessary.
The
silicides in situ, which can be difficult to control.11
A
65 continuous input of energy through the grinding process drives
the the reaction to completion.
controllable route to unfunctionalized silicides would allow a top
down approach to forming SiGe alloys enhanced with silicide
40 inclusions.
Zirconium disilicide was prepared by ball milling
a
stoichiometric amount of zirconium (IV) chloride (Strem
Chemicals, 99.6%) with calcium silicide (CaSi) (GFS Chemicals,
Traditional routes to producing zirconium disilicide include
silicothermic reduction 12, electrochemical 13, mechanochemical 70 Inc., 99.5%), or mechanochemically synthesized CaSi in an argon
14, sintering 15, arcꢁmelting 15, and selfꢁpropagating metathesis
reactions 16, 17. However, these reactions are difficult to scale, do
45 not yield pure ZrSi2, and do not allow for control of crystallite
size. In addition, some routes require temperatures above
1000ºC.
environment. Calcium chloride (Bryant Lab, Inc.) was used as a
diluent to control the size of the ZrSi2 crystallites. Milling
experiments were carried out using 8000M and 8000D SPEX
CertiPrep mixer/mills. Three 440c stainless steel balls (1.27ꢁcm
75 dia., 8g ea.) were used as the milling media. Commercial
calcium silicide contains a significant amount of iron impurities.
This study focuses on an alternative synthetic route to ZrSi2
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

ChemComm
Page 2 of 3
View Article Online
. Synthesis by a
14
27
In order to reduce these impurities,25 calcium silicide was 30 reaction times
or yield impure materials
mechanochemically prepared from the elements using a method
similar to that reported for Mg2Si.26 One gram of calcium
(granules, redistilled ꢁ6 mesh, 99.5% Alfa Aesar) was added in
three increments to a stoichiometric quantity of silicon (Virgin
mechanically driven metathesis reaction (Equation 1) remedies
these deficiencies. Zirconium silicide has been previously
synthesized via a selfꢁpropagating solidꢁstate metathesis (SSM)
reaction at elevated temperatures. This is the first time such a
5
poly fines 99.999%, Alfa Aesar, ground and sieved to ꢁ270 mesh 35 reaction has been performed at nominally ambient conditions.
under argon). Grinding for 30 minutes in a steel SPEX vial
followed each calcium addition. Size controlled ZrSi2 was
prepared by milling 2 g reaction masses for 8 h in 30ꢁminute
ZrCl4 + 2CaSi → ZrSi2 + 2CaCl2
(1)
10 increments, followed by 30 min of cooling to reduce wear on the
An added benefit, to this approach, is that it is possible to scale
mill’s motor. The product was isolated in an argon environment 40 mechanochemical reactions through modification of mill design.
28
to prevent oxygen contamination.
The crystallite size of ZrSi2 was controlled by the addition of
an inert diluent, CaCl2. Figure 1 shows the XRD patterns of
ZrSi2 at different diluent loadings. Size analysis was performed
using the Scherrer method. As the diluent amount was increased,
45 the crystallite size decreased. This allowed for the preparation of
nanocrystalline materials ranging from 9ꢁ30 nm. Figure 2 shows
that the crystallite size of ZrSi2 obtained is dependent upon the
concentration of ZrCl4 used. The reactor volume is fixed at 65
mL and concentration is defined as moles of reagent per liter of
50 free volume of the vessel (total volume excluding the volumes of
the milling media and reactants). This has been successfully
applied to the kinetic analysis of the mechanochemical formation
of alkaline earth carbides.25 As ZrCl4 concentration was
increased, the crystallite size of the synthesized ZrSi2 increased
55 linearly. This analysis approach is a departure from the typical
mechanochemical reaction analysis, which characterizes reactions
in terms of ball to reactant ratios.29 Although this method takes
into account the increase in the kinetic energies available by
using more or larger balls, it does not take into account the
60 restriction in motion by increased ball volumes. The analysis
presented here takes both into account for a single ball material.
The addition of CaCl2 reduced the effect of Ostwald ripening and
resulted in smaller crystallite sizes. It is important to note that
none of these reactions selfꢁpropagate. The continuous input of
65 energy from milling is required for the reaction to go to
completion.
Formamide (Aldrich, 99%) and N,Nꢁdimethylformamide
Figure 2. Control of the average crystallite size in the mechanochemical
15 synthesis of ZrSi2. The concentration of ZrCl4 is expressed in terms of
moles/liter of free volume.
(DMF, Acros, 99.8% extra dry) were used to wash away the
calcium chloride byꢁproduct. The formamide was dried over
molecular sieves (4ꢁ8 mesh, Acros) prior to use. The reaction
20 mass was transferred to a 100ꢁmL serum vial along with 15 mL
of formamide, crimped with a cap and septum, and centrifuged at
3000 rpm using an RCꢁ5 Superspeed Refrigerated Centrifuge.
The supernatant was decanted in an argon atmosphere and this
process was repeated twice. N,Nꢁdimethyl formamide (in three
25 15 mL portions) was used to rinse off the remaining formamide.
The DMF was removed by heating under vacuum inside a glove
box.
In order to remove the diluent and byꢁproduct (CaCl2), the
product required a washing step under argon to prevent surface
oxidation. The solvent must be polar enough to dissolve CaCl2,
70 but not possess –OH groups. Past reports have used dilute acid to
13, 30
remove byꢁproducts and obtain a pure silicide product
.
Mechanochemical routes to zirconium silicide from the
elements have been reported, however these routes required long
However, washing with water or aqueous acids introduces
Figure 3. Transmission electron microscope images of ZrSi2 prepared mechanochemically from a reaction diluted 50 mass% with CaCl2. The material
was isolated airꢁfree using formamide: a) particles range from 100 nm to 20 nm; b) each particle is composed of crystalline regions as small as 5 nm in
diameter; c) elemental analysis shows that calcium chloride was effectively removed. The remaining calcium is due to calcium oxide in the starting
material.
2
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 3 of 3
ChemComm
View Article Online
3. V. S. Neshpor and G. V. Samsonov, Dokl. Akad. Nauk SSSR, 1960,
134, 1337ꢁ1338.
4. A. Memarpour, V. Brabie and P. G. Joensson, ISIJ Int., 2010, 50,
1612ꢁ1621.
65 5. O. N. Grigoriev, B. A. Galanov, V. A. Kotenko, S. M. Ivanov, A. V.
Koroteev and N. P. Brodnikovsky, J. Eur. Ceram. Soc., 2010, 30,
2173ꢁ2181.
6. K. Pomoni and J. Salmi, J. Phys. D: Appl. Phys., 1991, 24, 727ꢁ730.
7. I.ꢁJ. Cho, K.ꢁT. Park, S.ꢁK. Lee, H. H. Nersisyan, Y.ꢁS. Kim and J.ꢁ
H. Lee, Chemical Engineering Journal, 2010, 165, 728ꢁ734.
8. Y. Ma, R. Heijl and A. C. Palmqvist, Journal of Materials Science,
2012, 1ꢁ12.
9. H. J. Kim, in 47th AIAA/ASME/SAE/ASEE Joint Propulsion
Conference & Exhibit 9th Annual International Energy Conversion
Engineering Conference, AIAA/ASME/SAE/ASEE, San Diego, CA,
2011, vol. Manuscript ID: 1027521.
10. N. Mingo, D. Hauser, N. P. Kobayashi, M. Plissonnier and A.
Shakouri, Nano Letters, 2009, 9, 711ꢁ715. KumakuraKumakura
11. W. Luo, H. Li, Y. Yan, Z. Lin, X. Tang, Q. Zhang and C. Uher,
Intermetallics, 2011, 19, 404ꢁ408.
12. A. V. Tkachenko and T. Y. Kosolapova, Powder Metallurgy and
Metal Ceramics, 1968, 7, 178ꢁ181.
13. V. V. Malyshev, N. N. Uskova and V. I. Shapoval, Powder Metall.
Met. Ceram., 1997, 36, 289ꢁ292.
85 14. Y. Bing K, Journal of Alloys and Compounds, 1998, 268, 266ꢁ269.
15. J. Canel, J. Zaman, J. Bettembourg, F. M. Le and S. Poissonnet, Int.
J. Appl. Ceram. Technol., 2006, 3, 23ꢁ31.
16. I. P. Parkin, Chemical Society Reviews, 1996, 25, 199ꢁ207.
17. R. M. Jacubinas and R. B. Kaner, Mater. Res. Soc. Symp. Proc. ,
1994, 322, 133ꢁ137.
18. E. Ivanov and C. Suryanarayana, Journal of Materials Synthesis and
Processing, 2000, 8, 235ꢁ244.
surface oxides and hydroxides. It is known that ZrSi2 forms a
31
stable colloid in water due to surface oxidation.
Using an
alternative washing method, which produces a material suitable
for conductive composites, minimized surface oxidation. With a
high dielectric constant, formamide is the preferred solvent for
CaCl2 removal. Dimethylformamide can also be used, but the
removal of CaCl2 is much less efficient due to its lower polarity.
The CaCl2 byꢁproduct was completely removed when formamide
was used as an extraction solvent. The EDS spectrum, Figure 3,
10 has no detectable chlorine peaks implying an upper limit of 1 at%
for the chlorine content. A small amount of CaO impurity was
also present; this may be due to the presence of CaO in the
commercially obtained CaSi. Figure 3 also shows a TEM image
obtained from a reaction with 50% diluent loading. Mechanically
15 driven reaction can suffer from iron contamination when steel is
used for the media and reaction vessel. Using ironꢁfree milling
materials such as alumina and tungsten carbide can eliminate this.
However, there were no measureable iron peaks in the EDS
spectrum, implying an upper limit for iron contamination of 1
20 at%. The particle size ranged from 20 nm to 100 nm with
crystalline regions as small as 5 nm.
In conclusion, unfunctionalized zirconium disilicide
nanomaterials of varying sizes were synthesized through a
mechanochemical metathesis reaction. The crystallite sizes
25 ranged from 9 to 30 nm depending on the amount of diluent used.
Removal of the diluent and salt product using formamide resulted
in isolation of polydisperse nanoparticles without capping groups
or a passivating oxide layer. Oxygenꢁfree ZrSi2 could be
produced by utilizing ultrapure CaSi. This would allow for
30 nanoelectroceramic particles of the desired size to be
incorporated into a composite as a reinforcement material for the
improvement of high temperature thermoelectric materials and a
variety of other applications.
5
70
75
80
90
19. P. G. McCormick, T. Tsuzuki, J. S. Robinson and J. Ding, Advanced
Materials, 2001, 13, 1008ꢁ1010.
95 20. P. Baláž, E. Boldižárová, E. Godočıková and J. Briančin, Materials
Letters, 2003, 57, 1585ꢁ1589.
21. C. Chakurov, V. Rusanov and J. Koichev, Journal of Solid State
Chemistry, 1987, 71, 522ꢁ529.
22. J. Ding, T. Tsuzuki, P. G. McCormick and R. Street, Journal of
Alloys and Compounds, 1996, 234, L1ꢁL3.
23. J. Ding, T. Tsuzuki, P. G. McCormick and R. Street, Journal of
Physics D: Applied Physics, 1996, 29, 2365.
24. R. A. Janes, M. Aldissi and R. B. Kaner, Chemistry of Materials,
2003, 15, 4431ꢁ4435.
100
This work was supported in part by the Florida Space Institute
35 Space Research Initiative Program.
105 25. S. M. Hick, C. Griebel and R. G. Blair, Inorg. Chem., 2009, 48,
2333ꢁ2338.
Notes and references
26. S. K. Bux, M. T. Yeung, E. S. Toberer, G. J. Snyder, R. B. Kaner and
J.ꢁP. Fleurial, Journal of Materials Chemistry, 2011, 21, 12259ꢁ
12266.
a Department of Chemistry, University of Central Florida, Orlando, FL
32816, United States of America, Fax 01 407 823 2252; Tel 01 407 823
40 0639; E-mail: richard.blair@ucf.edu
110 27. P. Matteazzi, F. Miani, G. Le Caër and E. BauerꢁGrosse, Euromat 91;
Proceedings of the 2nd European Conference on Advanced Materials
and Processes, 1992, 2, 359.
28. A. V. Dushkin, Chem. Sust. Dev., 2004, 12, 251ꢁ273.
29. C. Suryanarayana Progress in Materials Science, 2001, 46, 1ꢁ184.
115 30. A. M. Nartowski and I. P. Parkin, Polyhedron, 2002, 21, 187ꢁ191.
31. E. Wedekind, Zeitschrift fuer Chemie und Industrie der Kolloide,
1911, 7, 249ꢁ251.
b Department of Mechanical, Materials and Aerospace Engineering,
University of Central Florida, Orlando, FL 32816, United States of
America.
c The National Center for Forensic Science, 12354 Research Parkway,
45 Ste. 225, Orlando, FL 32826, United States of America.
†This article is part of the ChemComm 'Mechanochemistry' web themed
issue.
‡ Powder Xꢁray diffraction (PXRD) was performed using a Rigaku
Multiflex thetaꢁtheta powder Xꢁray diffractometer with a copper source
50 (Cu Kαl = 1.5418Å). Diffractograms were collected from 5 to 80 degrees
2θ using 0.010ꢁdegree steps and 0.3 seconds of dwell time.
Transmission electron spectroscopy (TEM) and energyꢁdispersive Xꢁ
ray spectroscopy (EDS) were performed using an FEI Technai F30
transmission electron microscope operating at an accelerating voltage of
55 300 kV.
1. I.ꢁJ. Shon, J.ꢁH. Park, J.ꢁK. Yoon and H.ꢁK. Park, Mater. Res. Bull.,
2009, 44, 1462ꢁ1467.
2. I.ꢁY. Ko, J.ꢁH. Park, J.ꢁK. Yoon, K.ꢁS. Nam and I.ꢁJ. Shon, Ceram.
60
Int., 2010, 36, 817ꢁ820.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3