Nanocrystalline yttria-stabilized zirconia fibers from plant fibers and their polymer composites

Article abstract of DOI:10.1111/j.1551-2916.2007.02215.x

Nanocrystalline zirconia-8-mol% yttria (yttria-stabilized zirconia (YSZ): ZrO₂-8-m% Y₂O₃) fibers have been prepared from aqueous poly vinyl alcohol (PVA)-zirconium oxy nitrate solution and jute (plant fiber). Soluble Zr and Y ions in PVA solution formed a uniform coating on the surface of jute once it dried completely. Slow hydrolysis of zirconium ion with ammonium hydroxide deposited zirconium hydroxide on the jute surface. Decomposition of the dried zirconium hydroxide-coated jute at high temperature (1200°C/2 h) resulted in the formation of single-phase, nanocrystalline cubic-YSZ with the corresponding average X-ray crystallite size 30-35 nm. Heat-treated fibers have been characterized by X-ray diffraction and scanning electron microscopy. We also prepared polymer composites by incorporating chopped, ground YSZ fibers into epoxy matrix and investigated polymer/fiber interface by transmission electron microscopy analysis.

Full text of DOI:10.1111/j.1551-2916.2007.02215.x

J. Am. Ceram. Soc., 91 [3] 1034–1036 (2008)
DOI: 10.1111/j.1551-2916.2007.02215.x
r 2007 The American Ceramic Society
ournal
J
Nanocrystalline Yttria-Stabilized Zirconia Fibers from Plant Fibers and
their Polymer Composites
w,z,z,J
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z
Rabindra N. Das,
Sanjukta Nad, and Panchanan Pramanik
z
Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
yDepartment of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-1501
Nanocrystalline zirconia–8-mol% yttria (yttria-stabilized
zirconia (YSZ): ZrO –8-m% Y O ) fibers have been prepared
The process involves in-situ precipitation of yttrium–zirconium
hydroxides into the porous fibrous structure of jute. Heat treat-
ment of the plant fibrous mass in furnace air environment results
in YSZ fibers. YSZ chopped and ground fibers were also mixed
with epoxy matrix to fabricate polymer composites and inves-
tigated through transmission electron microscopy (TEM) stud-
ies. Polymer composites are key to the development of low cost,
high-performance materials for applications ranging from au-
tomotive to food packaging to tissue engineering. A major chal-
lenge for further development of polymer composites is the lack
of even simple structure–property models. The present objective
is to develop YSZ–epoxy composites, which can further be ex-
tended to fabricate proton exchange membrane (PEM) fuel cells
2
2
3
from aqueous poly vinyl alcohol (PVA)–zirconium oxy nitrate
solution and jute (plant fiber). Soluble Zr and Y ions in PVA
solution formed a uniform coating on the surface of jute once it
dried completely. Slow hydrolysis of zirconium ion with ammo-
nium hydroxide deposited zirconium hydroxide on the jute sur-
face. Decomposition of the dried zirconium hydroxide-coated
jute at high temperature (12001C/2 h) resulted in the formation
of single-phase, nanocrystalline cubic-YSZ with the correspond-
ing average X-ray crystallite size 30–35 nm. Heat-treated fibers
have been characterized by X-ray diffraction and scanning elec-
tron microscopy. We also prepared polymer composites by in-
corporating chopped, ground YSZ fibers into epoxy matrix and
investigated polymer/fiber interface by transmission electron
microscopy analysis.
1
5,16
where YSZ will be dispersed in the Nafion resin.
Jute is a plant fiber obtained from the bark of the plants.
Traditionally, jute is used as an industrial raw material for mak-
ing packaging materials. In this process, we have used jute as a
network for growing YSZ fibers. As far as we know, this is the
first time any plant fiber (jute) has been used to fabricate ceramic
fibers.
I. Introduction
ECENTLY, significant progress has been achieved in the
development of nanocrystalline zirconia to meet the grow-
R
conia exists in three polymorphs ; these are monoclinic (m)
1
–4
ing demand for high-performance engineering materials. Zir-
5
II. Experimental Procedure
tetragonal (t), and cubic (c). Among them tetragonal and cubic
phases are metastable forms but monoclinic is the stable form at
All the chemical reagents used in these experiments were
analytical grade. The raw materials that were used for the prep-
aration of YSZ (ZrO : 8 mol% Y O ) were zirconium oxychlo-
2 2 3
6
room temperature. Various dopants such as calcium oxide, sil-
7
8
ica, cerium oxide, yttrium oxide,
9,10
11
chromium oxide, niobi-
1
2
13
um oxide, tantalum oxide, tin oxide, etc., have been used to
14
ride (Aldrich Chemicals, Milwaukee, WI), yttrium oxide, poly
vinyl alcohol (PVA), jute, nitric acid, and ammonium hydroxide.
Zirconium oxychloride (Aldrich Chemicals) was dissolved in
a minimum quantity of distilled water. Zirconium hydroxide (or
hydrated zirconium oxide) was precipitated from zirconium
oxychloride solution by the addition of ammonium hydroxide.
The precipitate was filtered and washed several times. Zirconium
hydroxide was then dissolved in nitric acid solution. Similarly,
yttrium (99.9% Aldrich Chemicals) oxide was dissolved in nitric
acid to form yttrium nitrate solution. Appropriate amounts of
yttrium nitrate and zirconium nitrate were mixed with each oth-
er to produce precursor solution. About 1–10-cm well-separated
jute fiber was then soaked into the precursor solution with 10%
PVA solution for 24 h. After 1 day, the soaked fibers were dried
for 12–24 h to remove excess PVA and metal nitrate solution.
The dried fibers containing metal nitrate and PVA were again
soaked for 24 h into ammonium hydroxide solution. In the
presence of ammonium hydroxide, metal nitrates were hydro-
lyzed to yttrium–zirconium hydroxide, which was deposited
slowly on jute fiber. Heat treatment of the dried yttrium–zirco-
nium hydroxide containing jute fibers at 12001C for 2 h in a
muffle furnace resulted in the YSZ fibers. Figure 1 shows scan-
ning electron micrograph (SEM) photographs of the as-formed
mass of YSZ fibers. Fiber mass was chopped and ground to
powder, which was used for X-ray diffraction studies. X-ray
diffraction studies of fibers were performed using fully auto-
mated system (Philips, Eindhoven, the Netherlands). A setting
of 40 kV and 30 mA was applied to the CuKa target, with a step
size of 0.021 (2y) and a count time of 0.5 s per step.
2 3
stabilize metastable zirconia phases. Addition of Y O (yttria-
stabilized zirconia (YSZ)) results in the stabilization of the cubic
fluorite structure of ZrO . The high oxygen conductivity (0.1
2
ꢁ
1
(
O ꢀ cm) ) of YSZ (ZrO
2 2 3
:Y O ) at high temperatures (10001C)
has made this material one of the most extensively studied fast
anionic conductors for its applications in solid oxide fuel cells
31
(
SOFCs) and oxygen sensing devices. Yttrium (Y ) cations
41
replace some of the Zr ions that create oxygen vacancies
responsible for the ionic conduction. As far as the synthesis of
ceramics is concerned, there is an ever-growing need to develop
simple synthetic procedure from easily available raw materials.
Consequently, researchers in the field of material processing
have been looking at biological systems for inspiration. The
above factors, combined with academic curiosity, have led to the
development of bio-mimicking approaches for the growth of
advanced materials.
In this work, the authors report a novel chemical route for the
preparation of fiber like YSZ using aqueous PVA (10 wt%),
zirconium nitrate, yttrium nitrate, and jute (plant fiber).
S. Komarneni—contributing editor
Manuscript No. 23552. Received August 4, 2007; approved October 15, 2007.
Author to whom correspondence should be addressed. e-mail: rabinnd@yahoo.com
w
z
Author was also associated with Department of Materials Science and Engineering,
Cornell University.
Current address: EIT (Formerly IBM), Endicott, NY.
J
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034

March 2008
Communications of the American Ceramic Society
1035
Fig. 1. Scanning electron micrograph of yttria stabilized zirconia (YSZ) fibers (close up and wider view).
Suspensions of the YSZ fibers in an epoxy resin were formu-
lated by mixing appropriate amounts of YSZ fibers, bisphenol–
Heat treatment of the fibrous mass at 12001C for 2 h resulted
in the formation of single-phase YSZ (ZrO :Y O ) as deter-
2 2 3
s
epoxy resin (EPON 828, M B377), dicyanadiamide, and
mined by X-ray diffraction (XRD). However, the XRD lines of
these powders were broad indicating fine crystals. The size of the
n
2
-methylimidazole in N-methyl pyrrolidone (NMP). The mix-
tures were ultrasonicated for 25 min to yield homogeneous sus-
pensions. The suspensions were slowly evaporated for 12–24 h.
Partially evaporated mixtures were speed mixed at 3000 rpm for
3
min and were poured in teflon molds and the residual solvent
was evaporated in a vacuum oven at a temperature of 751C for
2 h to ensure complete drying. The dried composites were cured
7
under vacuum at a temperature of 1751C typically for 15 h.
III. Results and Discussion
Figure 1 shows the SEM microstructures of YSZ fibers
heat-treated at 12001C for 2 h. Fiber samples were strong, stiff,
and handleable, which are 1–10-cm long and 5-mm wide. SEM
shows some fiber agglomeration. Proper jute fiber processing
before soaking into the precursor solution possibly reduces fiber
agglomeration.
1400
1200
1000
800
600
400
200
0
0
10
20
30
40
50
60
70
Two Theta
Fig. 2. X-ray diffraction pattern of the precursor powder heat-treated
at 12001C/2 h using CuKa.
Fig. 3. Bright field electron micrograph of yttria-stabilized zirconia
(YSZ)–epoxy composites.

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Communications of the American Ceramic Society
Vol. 91, No. 3
Fig. 4. Tentative mechanism.
2
B. Xia, L. Duan, and Y. Xie, ‘‘ZrO
2
Nanopowders Prepared by Low-
crystals was determined from X-ray line broadening studies.
˚
Temperature Vapor-Phase Hydrolysis,’’ J. Am. Ceram. Soc., 83 [5] 1077–80
2000).
Using Scherrer’s formula and with l 5 1.54 A, the crystallite
(
size, t is estimated to be around 30–35 nm. Figure 2 shows a
room temperature XRD plot of the heat-treated YSZ fibers.
The finer details of the fibers and their morphology into
polymer matrix were investigated using a Philips TEM. The
bright field electron micrograph of YSZ–epoxy composites is
shown in Fig. 3. It consists of small submicrometer fibers about
3
A. Benedetti, G. Fagherazzi, and P. Francesco, ‘‘Preparation and Structural
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1989).
(
4
J. C. Ray, R. K. Pati, and P. Pramanik, ‘‘Chemical Synthesis of Nanocrystal-
line Zirconia by a Novel Polymer Matrix-Based Precursor Solution Method Using
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5
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03–4 (1975).
S. K. Saha and P. Pramanik, ‘‘Innovative Chemical Method for Preparation
300–500-nm long and around 100-nm wide uniformly distribut-
ed throughout the epoxy matrix.
6
Of Calcia Stabilized Zirconia Powders,’’ Br. Ceram. Trans., 94 [3] 123–7
1995).
Jute swells until the cell wall is saturated with water. Jute cell
wall polymers contain hydroxyl and other oxygen-containing
(
7
F. del Monte, W. Larsen, and J. D. Mackenzie, ‘‘Stabilization of Tetragonal
ZrO2 in ZrO2-SiO2 Binary Oxides,’’ J. Am. Ceram. Soc., 83 [3] 628–34
2000).
1
7
groups that attract water through hydrogen bonding. In our
case, we have used aqueous metal nitrate, PVA solution that can
easily interact with the jute cell wall either by hydrogen bonding
(
8
J. D. Lin and J. G. Duh, ‘‘Crystallite Size and Microstrain of Thermally Aged
Low-Ceria- and Low-Yttria-Doped Zirconia,’’ J. Am. Ceram. Soc., 81 [4] 853–60
(1998).
(
water and PVA) or by complex formation (zirconium, yttrium
9
Y.-H. Lee, C.-W. Kuo, and I-M Hung, ‘‘The Thermal Behavior of 8 mol%
Yttria-Stabilized Zirconia Nanocrystallites Prepared by a Sol–Gel Process,’’
ion). Treatment of ammonia slowly hydrolyzes Y and Zr ions
and precipitates yttrium zircoium hydroxide on the jute cells.
PVA not only reduces hydrolysis process but also acts as a
binder to stick zirconium hydroxide within the cell region. Heat
treatment of jute grows nanocrystalline YSZ from individual
cells and maintains the fiber’s structure. Figure 4 shows a ten-
tative mechanism for fiber formation.
J. Non-Cryst. Solids, 351 [49–51] 3709–15 (2005).
J. C. Ray, R. K. Pati, and P. Pramanik, ‘‘Chemical Synthesis and Structural
10
Characterization of Nanocrystalline Powders of Pure Zirconia and Yttria Stabi-
lized Zirconia (YSZ),’’ J. Eur. Ceram. Soc., 20 [9] 1289–95 (2000).
J. C. Ray, C. R. Saha, and P. Pramanik, ‘‘Stabilized Nanoparticles of Meta-
11
31
41
stable ZrO
the Study of the Thermal and Structural Properties,’’ J. Eur. Ceram. Soc., 22 [6]
51–62 (2002).
2
with Cr /Cr Cations: Preparation from a Polymer Precursor and
8
12
J. C. Ray, A. B. Panda, C. R. Saha, and P. Pramanik, ‘‘Synthesis of Niobi-
um(V)-Stabilized Tetragonal Zirconia Nanocrystalline Powders,’’ J. Am. Ceram.
Soc., 86 [3] 514–6 (2003).
IV. Conclusion
13
J. C. Ray, A. B. Panda, and P. Pramanik, ‘‘Chemical Synthesis of Nanocrys-
tals of Tantalum Ion-Doped Tetragonal Zirconia,’’ Mater. Lett., 53 [3] 145–50
2002).
In conclusion, YSZ fibers have been prepared from the thermal
decomposition of the dried PVA–metal hydroxide-coated jute
mass. In this paper, we introduced plant fibers to produce ce-
ramic fibers for the first time. This kind of YSZ fiber is expected
to play a key role in the future development of low cost, high-
(
14
J. C. Ray, C. R. Saha, and P. Pramanik, ‘‘Chemical Synthesis of Nanocrys-
talline Tin-Doped Cubic ZrO2 Powders,’’ Mater. Lett., 57 [13–14] 2140–4
2003).
(
15
1
8,19
M. Watanabe, H. Uchida, and M. Emori, ‘‘Analyses of Self-Humidification
and Suppression of Gas Crossover in Pt-Dispersed Polymer Electrolyte Mem-
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performance electrolyte membranes for SOFCs.
The current
work also demonstrates the dispersion of YSZ fibers into epoxy
matrix. TEM analysis of the composite shows uniform YSZ fi-
ber dispersion into polymer matrix. The synthetic strategy pre-
sented here may be extended to other metal oxide systems of Ti,
Nb, V, Si, Mn, W, Mo, etc.
16
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(
17
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(2000).
18
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