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 Novel Processing of
Ceramics and Composites
 Novel Processing of
Ceramics and Composites

Ceramic Transactions Series, Volume 195

Proceedings of the 6th Pacific Rim Conference on

Ceramic and Glass Technology (PacRim6);
September 11-16, 2005; Maui, Hawaii

Edited by
Narottam P. Bansal
J. P. Singh
James E. Smay
Tatsuki Ohji

l^INTERSCIENCE
A JOHN WILEY & SONS, INC., PUBLICATION
Copyright © 2006 by the American Ceramics Society. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or
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ISBN-10 0-470-08389-1

Printed in the United States of America.

10 9 8 7 6 5 4 3 2 1
 Contents

Preface ix

Chemical Vapor Deposition

High Speed Deposition of YSZ Films by Laser Chemical Vapor 3

Deposition
Teiichi Kimura and Takashi Goto

Preparation of Ru-C Nano-Composite Films and Their Electrode 13

Properties for Oxygen Sensors
Teiichi Kimura and Takashi Goto

Combustion Synthesis

Synthesis of Sm0.5Sr0i5CoO3_x and La0.6Sr0i4CoO3_x Nanopowders 23

by Solution Combustion Process
Narottam P. Bansal and Zhimin Zhong

Chemistry Purification of Titanium Diboride Powder Synthesised 33

by Combustion Synthesis Processes
Wang Weimin, Fu Zhengyi, and Wang Hao

Reaction Forming

Fabrication of Silicon Carbide From Bamboo Carbon Templates 45

Yung-Jen Lin and Yi-Hsiang Chiu
Effects of Process Parameters on Post Reaction Sintering of Silicon 57
Nitride Ceramics
Toru Wakihara, Junichi Tatami, Katsutoshi Komeya, Meguro Takeshi, Hideki Kita,
Naoki Kondo, and Kiyoshi Hirao

Polymer Processing

Synthesis of Carbon/Fe-Ni-Cu Alloy Composite by Carbonization 67

of Organometallic Polymers and Their Magnetic Properties
Yukiko Uchida, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Akinori Muto,
and Yusaku Sakata

Electochemical Deposition

Fabrication of YSZ Thin Films in an Aqueous Solution by Electro- 77

Chemical Deposition
Atsushi Saiki, Hiroki Uno, Satoka Ui, Takashi Hashizume, and
Kiyoshi Terayama

Plasma Synthesis

Preparation and Characterization of Epitaxial Fe2_xTix03 Solid 87

Solution Films
Tatsuo Fujii, Hideki Hashimoto, Yusuke Takada, Makoto Nakanishi,
and Jun Takada

Solid Freeform Fabrication

Microtomography of Solid Freeform Fabrication 97

Jay C. Hanan, James E. Smay, Francesco DeCarlo, and Yong Chu

Floc-Casting

Fabrication and Evaluation of Transparent Amorphous Si0 2 107

Sintered Body Through Floc-Casting
D. Hiratsuka, J. Tatami, T. Wakihara, K. Komeya, T. Meguro, and
M. Ibukiyama

Solution Deposition

Yttria Stabilized Zirconia Thin Films Formation From an Aqueous 115

Solution by Mist Deposition
Atsushi Saiki, Yukimine Fujisawa, Takashi Hashizume, and Kiyoshi Terayama

vi • Novel Processing of Ceramics and Composites

Nanopowders and Nanorods

Synthesis and Structural Characterization of Nanoapatite Ceramics 125

Powders for Biomédical Applications
Kanae Ando, Mizuki Ohkubo, Satoshi Hayakawa, Kanji Tsuru, Akiyoshi Osaka,
Eiji Fujii, Koji Kawabata, Christian Bonhomme, and Florence Babonneau

Novel Process of Submicron-Scale Ceramic Rod Array Formation 133

on Metallic Substrate
Kazuya Okamoto, Satoshi Hayakawa, Kanji Tsuru, and Akiyoshi Osaka

Coatings and Films

Novel Process for Surface Treatment of AIN - Characterization and 141

Application
Takehiko Yoneda, Motonobu Teramoto, Kazuya Takada, and
Hiroyuki Fukuyama

Novel Process for Surface Treatment of AIN—High-Temperature 149

Oxidation Behavior of AIN
Hiroyuki Fukuyama, Tetsuharu Tanoue, and Kazuhiro Nagata

MYCRONID™ Based Long-Lasting BN Hardcoating as Release 159

Agent and Protection Against Corrosion for Aluminum Foundry
Applications
Jochen Greim, Martin Engler, Krishna Uibel, and Christoph Lesniak

Composites

A Study into Epoxy Composites for High-Voltage Device 169

Encapsulation
Ammer K. Jadoon, John C. Fothergill, and Andy Wilb
y
Qeopolymers

Advances in Understanding the Synthesis Mechanisms of New 187

Geopolymeric Materials*
Kenneth J.D. MacKenzie, Dan Brew, Ross Fletcher, Catherine Nicholson,
Raymond Vagana, and Martin Schmücker

Author Index 201

"Paper presented at the 107th Annual Meeting of The American Ceramic Society, April 10-13,
2005, Baltimore, Maryland

Novel Processing of Ceramics and Composites • vii

 Preface

An international symposium, "Novel Processing of Ceramics and Composites" was

held during the 6th Pacific Rim (PacRim-6) Conference on Ceramic and Glass
Technology in Kapalua, Maui, Hawaii, during September 11-16, 2005. This sym-
posium provided an international forum for scientists, engineers, and technologists
to discuss and exchange state-of-the-art ideas, information, and technology on ad-
vanced methods and approaches for processing and synthesis of ceramics, glasses,
and composites. A total of 56 papers, including four invited talks, were presented in
the form of oral and poster presentations indicating continued interest in the scien-
tifically and technologically important field of ceramic processing. Authors from 15
countries (Australia, Brazil, Canada, China, France, Germany, India, Italy, Japan,
Korea, Spain, Taiwan, Turkey, United Kingdom, and the United States) participat-
ed. The speakers represented universities, industries, and government research lab-
oratories.
These proceedings contain contributions on various aspects of synthesis and pro-
cessing of ceramics, glasses, and composites that were discussed at the symposium.
Eighteen papers describing the latest developments in the areas of combustion syn-
thesis, reaction forming, polymer processing, solid freeform fabrication, chemical
vapor deposition, electrochemical and solution depositions, plasma synthesis and
floc-casting for fabrication of nanopowders, nanorods, electronic ceramics, com-
posites, thin films, coatings, etc. are included in this volume. Each manuscript was
peer-reviewed using the American Ceramic Society review process.
The editors wish to extend their gratitude and appreciation to all the authors for
their cooperation and contributions, to all the participants and session chairs for
their time and efforts, and to all the reviewers for their useful comments and sug-
gestions. Financial support from the American Ceramic Society is gratefully ac-
knowledged. Thanks are due to the staff of the meetings and publications depart-
ments of the American Ceramic Society for their invaluable assistance.

ix
 It is our earnest hope that this volume will serve as a valuable reference for the
researchers as well as the technologists interested in innovative approaches for syn-
thesis and processing of ceramics, composites, nanopowders, nanorods, thin films,
coatings, etc.

NAROTTAM P. BANSAL
J. P. SINGH
JAMES E. SMAY
TATSUKI OHJI

x • Novel Processing of Ceramics and Composites

 Novel Processing of Ceramics and Composites
Edited by Narottam P. Bansal, J. P. Singh, James E. Smay and Tatsuki Ohji
Copyright © 2006 The American Ceramics Society

Chemical Vapor Deposition

 Novel Processing of Ceramics and Composites
Edited by Narottam P. Bansal, J. P. Singh, James E. Smay and Tatsuki Ohji
Copyright © 2006 The American Ceramics Society

HIGH SPEED DEPOSITION OF YSZ FILMS BY LASER CHEMICAL VAPOR

DEPOSITION

Teiichi Kimura and Takashi Goto

Institute for Materials Research, Tohoku University
2-1-1 Katahira, Aoba
Sendai, Miyagi, Japan 980-8577

ABSTRACT
Partially yttria-stabilized zirconia (YSZ) films were prepared by laser chemical vapor
deposition (LCVD). The assistance of laser increased the deposition rate for YSZ films up to
660 u.m/h. The increase in the deposition rate was accompanied by plasma formation around the
deposition zone, and the plasma was observed over critical laser power and substrate pre-heating
temperature. A wide variety of morphologies of films from feather-like columnar to dense
textures were obtained depending on deposition conditions. The columnar texture contained a
large amount of nano-pores at columnar boundary and inside grains. These columnar texture
and nano-pores were advantageous for applying YSZ films to thermal barrier coatings.

INTRODUCTION

Laser chemical vapor deposition (LCVD) has been utilized to fabricate mainly thin films
in semiconductor devise applications '. In general, LCVD can be categorized into two types; one
is photolytic LCVD where laser is used as a high-energy source for photochemical reactions and
the other is pyrolytic LCVD where laser is used as a heat-source for thermal reactions.
Photolytic LCVD would often adopt ultra-violet laser with energy of several eV. The chemical
reactions for the film deposition would proceed by high energy photon energy even without
substrate heating. In pyrolytic LCVD, on the other hand, significantly high deposition rates have
been achieved by focusing laser beam. However, the volume deposition rate (deposition rate in
thickness multiplied by area) has been very small ranging around 10"12 to 10"8 m h"', where thin
films, small dots and thin wires have been prepared 2. A CO2 laser with high power about
several 100 W was employed in LCVD to prepare relatively thick materials such as TiN and
TÍB2 several 10 urn in thickness 2. However, pyrolytic LCVD using the CO2 laser has not been
widely utilized due to several difficulties such as absorption by window material; ZnSe could be
commonly chosen to avoid absorption of an infra-red light.
We have found that many oxide thick films can be prepared at high deposition rates more
than several 100 um/h by using LCVD 3'4. This paper focuses on the preparation of yttria-
stabilized zirconia (YSZ) films by LCVD using high power Nd:YAG laser.
Since YSZ films are chemically stable at high temperatures having a low thermal
conductivity and good compatibility with Ni-base superalloy, they have been intensively
investigated as thermal barrier coatings (TBCs) 5. The thickness of TBCs should be more than
several 100 urn, and therefore high-speed deposition processes commonly atmospheric plasma
spray (APS) 6 and electron-beam physical vapor deposition (EBPVD) 7 have been employed.
However, another route for high-speed deposition should be pursued to develop higher

3
High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

Fig. 1 A schematic diagram of LCVD apparatus.

performance YSZ coatings. We have reported high-speed deposition of YSZ films at 108 u,m/h
by using conventional thermal MOCVD 8. However, the CVD process with much higher
deposition rates would be required for practical applications. In this paper, we report the high-
speed deposition of YSZ films by LCVD, and describes the effect of deposition conditions
mainly on deposition rates, morphology and nano-structure.

EXPERIMENTAL

Fig. 1 demonstrates a schematic diagram of LCVD apparatus that was made of stainless
steel with a hemispherical cold-wall type chamber. The laser light (Nd:YAG, continuous mode,
X = 1063 nm) was introduced into the chamber through a quartz window. The laser beam
expanded to about 25 mm in diameter was emitted to the whole AI2O3 substrate (polycrystalline,
15x 15x2 mm). The laser power (PL) was changed from 0 to 250 W. ß-diketone complexes, Zr
(dpm)4 (dpm: dipivaloylmethanate) and Y (dpm)î were used as precursors. Although we have
changed the Y2O3 content in YSZ films from 1 to 8 mol% by controlling the precursor
temperature, the results of 4 mol% Y2O3 are described hereafter. O2 gas was separately
introduced by a double tube nozzle and mixed with the precursor vapors around the substrate.
The substrate temperature (Tsub) was measured by a R-type thermocouple attached underneath
the substrate surface. The total pressure (PIot) was kept at 0.93 kPa.
Surface and cross-sectional morphologies were observed by scanning electron
microscopy (SEM). Transmission electron microscopy (TEM) was employed to investigate the
nano-structure of films. The crystal structure and preferred orientation were determined by X-
ray diffraction (XRD), and the composition was estimated by electron probe X-ray microanalysis
(EPMA).

4 • Novel Processing of Ceramics and Composites

 High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

300 500 700 900 1100

Pre-heating Temperature, Tpre/ K

Fig. 2 Effects of laser power (PL) and substrate pre-heating temperature (Tprc) on the deposition rate of
YSZ films.

RESULTS AND DISCUSSION

Fig. 2 demonstrates the effects of laser power (Pi ) and substrate pre-heating temperature
(Tpre) on the deposition rates. While almost no deposition occurred below PL = 50 W, significant
increase in deposition rates were observed above PL = 100W. The deposition rates of YSZ films
by thermal MOCVD have been commonly reported as few to several 10 pm/h; however, we
have achieved a deposition rate of 108 pm/h by using cold-wall type CVD and the ß-diketone
precursors [8]. LCVD, on the other hand, has attained a deposition rate more than several 100
pm/h. The deposition rate increased with increasing Tprc and Pi., and showed maximum at Pi. =
200 W and Tpre = 823 K. The decrease in the deposition rate at higher Tpre could be resulted
from the premature powder formation in a gas phase. A strong plasma emission was appeared
and accompanied with the increase in deposition rates above a critical PL. According to our
plasma diagnosis, the plasma had an electron temperature of 4000 K with a continuous spectrum
similar to the plank distribution 9. The substrate temperature was significantly increased
accompanying the plasma formation. Fig. 3 demonstrates the time dependence of substrate
temperature (Tsuh) after the laser emission and introduction of precursor vapors. Increases in
Tsub of 150 to 200 K were identified after the laser emission. Since the laser power would have
more capability to increase the Tsub, the laser might be partially reflected from the AI2O3
substrate surface resulting to rather small increase in the T^b- After the T^b was stabilized, the
precursor vapors and O2 gas were introduced, and after a minute an abrupt temperature increase
accompanying the plasma formation was identified. Fig. 4 demonstrates the effect of Ts„b on the
deposition rate of YSZ films comparing with literature data of conventional MOCVD l0"13, where
the results of relatively high-speed deposition of YSZ films were chosen. YSZ films have been
widely prepared by MOCVD owing to their useful applications as oxide ion conducting solid
electrolyte 14"16 and buffer layers for high-temperature superconducting oxides 17' 18. The
deposition rate was generally several pm/h in literatures; meanwhile high-speed deposition of

Novel Processing of Ceramics and Composites • 5

High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

200 W
1100
Plasma formation oo w
- 900
K

3 700

a.
E 500 Laser emission

300

50 100 150 200

Time, f/s

Fig. 3 Time dependence of substrate temperature (T^i,) after the laser emission and introduction of
precursor vapors.

Substrate temperature, 7SUb / K

13001200 1100 1000 900 800

0.9 1.0 1.1 1.3

Tsub"1/10-3K-1

Fig. 4 Effect of substrate temperature (T5Ub) on the deposition rate of YSZ films comparing with
literature data of conventional MOCVD (PL> 100 W).

6 • Novel Processing of Ceramics and Composites

 High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

YSZ films by MOCVD has been recently reported due to strong requirements for the application
to TBCs. The deposition rate generally increases with increasing Ts„b in MOCVD. The
activation energy in a low temperature region could be more than several 10 kj/mol, suggesting a
chemical reaction limited process 19. The activation energy decreases to several kJ/mol with
further increase in Tsub, suggesting a mass transfer (mainly source gas supply) limited process |l).
The deposition rates might be decreased at further higher temperatures due to premature powder
formation in a gas phase. In the present LCVD, the activation energy was 9 kj/mol in the
temperature range between TSUb = 800 and 1300 K, implying the mass transfer limited process. It
can be assumed that the plasma would enhance the reactivity of precursor vapors and the surface
mobility of chemical species could be also accelerated by the laser emission. The highest
deposition rate increased to 660 um/h by increasing the source flux, corresponding to the mass
transfer limited process of the present LCVD.
Figs 5 to 8 depict the cross-sectional texture of YSZ films. The YSZ film prepared at PL
= 100 W and Tsub - 893 K (Fig. 5) had a fine grained dense texture with insignificant preferred
orientation. Fig. 6 shows the YSZ film prepared at PL = 150 W and Tsub = 953 K with (200)
oriented cauliflower-like texture. Well-developed columnar texture with strongly (200) oriented
YSZ films were obtained at PL = 100 W and Tsllb = 1123 K (Fig. 7). The YSZ films prepared at
higher temperature (PL = 250 W, Tsl,b = 1213 K) had wider columnar grains (Fig. 8).
The cross-section of columnar texture for the YSZ film prepared at Pi = 200 W and T5ub
= 1173 K was observed by TEM as shown in Fig. 9. The gaps of about 100 nm in width and a
feather-like texture were observed near the surface (Fig. 9(a)). The feather-like texture has been
commonly observed in YSZ films prepared by EB-PVD 20 and plasma-enhanced CVD (PECVD)
2I
. Fig. 9 (b) demonstrates the nano-structure of middle of columnar texture, where voids about
10 nm in size and a large amount of nano-pores about a few nm in size were observed at the
columnar boundary and inside the grains, respectively. Fig. 9 (c) represents the nano-pores

Fig. 5 Cross-section of YSZ films prepared at P,.=100 W and Tsub=893 K

Novel Processing of Ceramics and Composites • 7

High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

Fig. 6 Cross-section of YSZ films prepared at P|.= 150 W and Tsul,=953 K

Fig. 7 Cross-section of YSZ films prepared at P[ =100 W and Ts,,i,=l 123 K

8 • Novel Processing of Ceramics and Composites

 High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

Fig. 8 Cross-section of YSZ films prepared at PL=250 W and T„b=1213 K

around the YSZ/substrate interface. Fine grained poly-crystalline grains with nano-pores were
observed around the interface. It is generally known that the te.xture in CVD would change from
fine grains with no specific orientation to significantly oriented columns with increasing the
thickness of films ", as typically depicted in Fig. 9.
The nano-pores inside grains were effective to improve the performance of YSZ films
for the application to TBCs 22. Fig. 10 shows the effect of deposition rates on the thermal

Fig. 9 Nano-structure of YSZ film prepared at Pi=200 W and Ts„b=1200 K, (a): near thefilmsurface,
(b): middle of the film, (c): near the substrate

Novel Processing of Ceramics and Composites • 9

High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

¿ 2.0
1
? 1.5

.> 1 0
tí
TJ

§ 0.5
to

2 o.o
•- 0 100 200 300 400 500
Deposition rate, RI Jim h"1

Fig. 10 Effect of deposition rates on the thermal conductivity of YSZ films prepared by LCVD.

conductivity of YSZ films prepared by LCVD. The thermal conductivity of YSZ films
decreased with increasing deposition rate. The thermal conductivity of the YSZ iilm prepared at
R=50 um/h (PL=I00 W and 1^=893 K) was 1.3 W/m K, which is almost a half of that of bulk
cubic YSZ, while that prepared at R=450 um/h (PL=200 W and T5ub=1200 K) was 0.7 W/m K.
This value is almost the same level as those of practical TBCs fabricated by APS and EBPVD.
The nano-pores could be the main reason for the low conductivity by phonon scattering as
reported in YSZ coatings fabricated by EBPVD The nano-pores at the YSZ/substrate interface
combined with the columnar texture would yield excellent adherence of YSZ coatings on Ni-
base super-alloy substrates surviving 1200 heat-cycles between 773 and 1673 K 23.

CONCLUSIONS

As an alternate route for the high-speed deposition process of YSZ coatings, we have proposed a
laser CVD process, where the highest deposition rate of 660 u.m/h was attained. This speed is
almost competitive to those of practical APS and EBPVD. A plasma formation and an exothermic
reaction in LCVD have caused significant increase in deposition rates. The high deposition rates
have yielded a large amount of nano-pores in columnar grains resulting in the significantly lower
thermal conductivity of about 0.7 W/m K.

ACKNOWLEDGEMENT

This work was performed as a part of Nano-Coating Project sponsored by New Energy and
Industrial Technology Development Organization (NEDO), Japan.

10 • Novel Processing of Ceramics and Composites

 High Speed Deposition of YS2 Films by Laser Chemical Vapor Deposition

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Bonanos, N , Slotwinski, R. K., Steele B. C. H., Butler, E. P., "High Ionic-conductivity in
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Tiwari, P., Kanetkar, S. M., Sharan, S. and Narayan, }.,"In situ single chamber laser
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buffer layers", Appl. Phys. Lett., 57, 1578-1580(1990).
18
Ogale, S. B., Vispute, R. D., Rao, R. R.,"Pulsed excimer laser deposition YiBa2Cu307_x
superconductor films on silicon with laser-deposited Y-Zr02 buffer layer". Appl. Phys. Lett., 57,
1805-1807(1990).
19
Bryant, W. A.. "Fundamentals of Chemical Vapor-deposition", J. Mater. Sei., 12. 1285-1306
(1977).

Novel Processing of Ceramics and Composites • 11

High Speed Deposition of YSZ Films by Laser Chemical Vapor Deposition

Lu, T. L., Levi, C. G., Wadley, H. N. G. and Evans, A. G., "Distributed Porosity as a Control
Parameter for Oxide Thermal Barriers Made by Physical Vapor Deposition", J. Am. Ceram. Soc,
84, 2937-2976(2001).
21
Préauchat, B, and Drawin S., "Properties of PECVD-Deposited Thermal Barrier Coatings",
Surf. Coatings Tech., 142-144, 835-842(2001).
22
Clarke, D.R. and Levi C. G., "Materials Design for the Next Generation Thermal Barrier
Coatings", Annu. Rev. Mater. Res., 33, 383-417 (2003).
23
Tu, R. and Goto, T., "Thermal Cycle Resistance of Yttria Stabilized Zirconia Coatings
Prepared by MO-CVD", Mater. Trans., 46, 1318-1323(2005).

12 • Novel Processing of Ceramics and Composites

 Novel Processing of Ceramics and Composites
Edited by Narottam P. Bansal, J. P. Singh, James E. Smay and Tatsuki Ohji
Copyright © 2006 The American Ceramics Society

PREPARATION OF Ru-C NANO-COMPOSITE FILMS AND THEIR ELECTRODE

PROPERTIES FOR OXYGEN SENSORS

Teiichi Kimura and Takashi Goto

Institute for Materials Research, Tohoku University
2-1-1 Katahira, Aoba
Sendai, Miyagi, Japan 980-8577

ABSTRACT

Ru-C nano-composite films containing about 73 vol% of carbon were prepared by

MOCVD, and their microstructures and electrode properties were investigated. Ru particles of
5-20 nm in diameter were dispersed in amorphous C matrix. The AC conductivities associating
to the interface charge transfer between Ru-C composite electrode and YSZ electrolyte were
100-1000 times higher than that of Pt electrodes. The emf values of the oxygen gas concentration
cell constructed from the nano-composite electrodes and YSZ electrolyte showed the Nernstian
theoretical values at low temperatures around 500 K. The response time of the concentration cell
was 900 s at 500 K.

INTRODUCTION

Solid-electrolyte type oxygen sensors are widely used for monitoring oxygen
concentration in exhaust gas of automobiles and chemical plants because of their relatively
simple configuration and direct indication of oxygen content in ambient atmosphere. This type of
oxygen sensors is mainly constructed from a solid electrolyte and electrodes. Yttria-stabilized
zirconia (YSZ) is commonly used as a solid electrolyte due to high ionic conductivity and
mechanical strength. Electrodes should have high electronic conductivity, high chemical/thermal
stability and catalytic activity for the dissociation of oxygen molecules "3. Since platinum group
metals, particularly Pt, could satisfy these requirements, Pt electrodes have been generally
applied to the oxygen sensors. The operation temperature of usual Pt/YSZ/Pt sensor is above
1000 K due to low catalytic activity of Pt and slow charge transfer at electrode/electrolyte/gas
triple points at low temperatures. Since the low temperature operation of oxygen sensors is
strongly required, a new electrode material with high catalytic activity at low temperatures
should be developed.
Metal-organic chemical vapor deposition (MOCVD) can be suitable for preparing
electrodes because of its controllability of microstructure of films by changing deposition
conditions. Many kinds of metal films have been prepared by MOCVD, in which impurity C has
been often contained degrading the electrical conductivity 4 ' 5 . On the other hand, the carbon
phase has an advantage to hinder the grain growth of metals, and to form metal nano-particle
dispersed composite films. The co-deposited C would often enhance the catalytic activity as
reported in Pt-C catalysts. Thus, metal-C nano-composite electrodes having high catalytic
activity can be prepared by MOCVD.
In this study, Ru-C composite electrodes were prepared by MOCVD, and their
microstructures and electrode properties were investigated.

13
Preparation of Ru-C Nano-Composite Films and their Electrode Properties

Table 1 Deposition conditions

Ru-C
Precursor Ru(dpm)3
Vaporize temperature [K] 473
Total pressure [kPa] 0.93
Substrate temperature [K] 673
Ar gas flow rate [10 8 m V ] 33
0 2 gas flow rate flO"8 m3s"'l 6.8

EXPERIMENTAL

Ru-C films were prepared on silica glass and YSZ(8 mol%Y203-Zr02) substrates using a
horizontal hot-wall type MOCVD apparatus . Ru(dpm)3 (dpm: dipivaloylmethanato) was used
as precursors. Deposition conditions are summarized in Table 1. Compositions and crystalline
phases of films were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction
(XRD). Microstructures were investigated with a scanning electron microscope (SEM) and a
transmission electron microscope (TEM). The electrical properties were studied by AC
impedance spectroscopy with a two-probe method in the frequency range between 0.1 Hz and
10 Hz. The oxygen concentration cell was constructed with the Ru-C nano-composite film
electrodes and YSZ electrolyte. The electro-motive-force (emf) values were measured at
temperatures from 500 to 773 K by changing the oxygen partial pressure ratio from 1 to 5.

RESULTS AND DISCUSSION

Microstructure

Fig.l demonstrates XRD patterns of Ru-C composite films. There are a few narrow peaks
assigned to Ru and a broad peak around 26=20°. Average crystalline size of Ru estimated from
full width at half maximum of (100), (101) and (110) diffraction peak using the Scherrer's
equation was about 8 nm. The AES spectra of the composite films after surface etching by Ar
ions for 600 s indicated a significant amount of C in the films. The C contents in the films were
estimated by XPS analysis and was 73 vol%.
Ru-C composite films consisted of spherical grains of 50 nm in diameter as shown in
Fig.2. Fig.3 shows TEM images of Ru-C composite films. Dark particles of 5-20 nm in size
were dispersed in an amorphous matrix without pore or gap at the boundary. Hereafter, these
films are mentioned as Ru-C nano-composite.

Electrode properties

Fig.4 depicts the AC impedance spectrum of YSZ with Ru-C nano-composite electrodes
at 773 K. Two semicircles near the original point could be assigned to bulk and grain boundary
responses of YSZ substrate, because they were independent of electrodes. The associated
capacitances were 5.8 pF and 0.11 nF, respectively, close to reported values 7. The third

14 • Novel Processing of Ceramics and Composites

 Preparation of Ru-C Nano-Composite Films and their Electrode Properties

10 20 30 40 50 60 70 80
29 (CuKa) / deg.

Fig.l XRD pattern of Ru-C composite film

Fig.2 Surface SEM image of Ru-C composite film.

Fig.3 TEM images of Ru-C composite films, (b) is higher magnification of (a).

Novel Processing of Ceramics and Composites • 15

Preparation of Ru-C Nano-Composite Films and their Electrode Properties

200
1.3x10"7F
E
g 100
5.8x10"12F
1.1x10-10F
1
o ° ° °
Kl

100 200 300 400

Z'/Qm

Fig.4 AC impedance spectrum for Ru-C electrode deposited on YSZ electrolyte at 773 K.

I¿
• 473 K
1 10 . o 513 K y
▼ 533 K y
^ 8 V 563 K ¿s

fi
■f
CO
c
(D
■o 4 _
•*-*
c<D „
b
3
2 -
ü
0 - 4& i i i i

0 10 20 30 40 50
Applied voltage, Vapp/ kV nr 1

Fig.5 Current-voltage characteristics of Ru-C composite electrode at various temperatures.

semicircle in low frequency region was assigned to the response of charge transfer at the
electrode/YSZ interface due to a large capacitance of 0.1 u.F. The interfacial semicircle was
partially drawn below 600 K, because the electrical resistivity of YSZ becomes too high and the
frequency range was not enough to obtain the whole semicircles. The current-voltage
characteristics (Fig.5) were investigated to measure the whole resistivity, and the interfacial
conductivity was estimated by subtracting the bulk and grain boundary resistivities of substrate
from the whole resistivity.
Fig.6 summarizes temperature dependence of the interfacial conductivity. The interfacial
conductivity of Ru-C nano-composite electrode was 1000-10000 times higher than that of
reported Pt electrode 8. The high interfacial conductivities of the nano-composite electrodes

16 • Novel Processing of Ceramics and Composites

 Preparation of Ru-C Nano-Composite Films and their Electrode Properties

Temperature, 77 °C
500 400 300 200
-3 i 1 r-

O Ru-C(th¡s work)
▲ Pt (Badwalle, 1979)
E
-5
ä
-6
o
-A_
-7
*^
f

-8 - * K

1.2 1.4 1.6 1.8 2.0 2.2

7-i/10-3K-i

Fig.6 Temperature dependence of Ru-C/YSZ intertacial conductivity.

30
>
- ' " ' O
E
UJ 20 . ' ' ' O
U_~

UJ
10 o Ru-C(This work)
Theoretical

n ■ <

400 500 600 700

Temperature, TI K
Fig.7 EMF values of the oxygen concentration cell using the Ru-C nano-composite electrodes
at 500 K.

Novel Processing of Ceramics and Composites • 17

Preparation of Ru-C Nano-Composite Films and their Electrode Properties

20

>
E
$
H" 10
LU

0
0 1 2 3 4 5
Time, f/ks

Fig.8 Time response of oxygen concentration cell using Ru-C nano-composite electrodes at 500
K.

could suggest the high catalytic activities of Ru nano-particles. The high interfacial conductivity
of Ru-C nano-composite could be mainly caused of the large effective surface area of Ru
particles in the nano-composite film without aggregation as shown in Fig, 2.
Fig.7 shows the emf values of the oxygen gas concentration cells using the nano-
composite electrodes. The Ru-C nano-composite electrodes showed the theoretical values even at
500 K. Fig.8 demonstrates the time response of the oxygen gas concentration cells using Ru-C
nano-composite electrodes. The response time of Ru-C electrode was 900 s at 500 K.

CONCLUSION

Ru-C nano-composite films containing about 73 vol% of carbon were prepared by MOCVD.
Ru particles of 5-20 run in diameter were dispersed in amorphous C matrix. The AC interface
electrical conductivities for Ru-C nano-composite electrodes were 1000-10000 times higher than
that of reported Pt electrode. The emf values of the oxygen gas concentration cell constructed
from Ru-C nano-composite electrodes showed the Nernstian theoretical values even at 500 K.
The response time of the concentration cell was 900 s at 500 K for Ru-C nano-composite
electrodes.

18 • Novel Processing of Ceramics and Composites

 Preparation of Ru-C Nano-Composite Films and their Electrode Properties

ACKNOWLEDGEMENT

This work has been financially supported by Japan Atomic Energy Research Institute, Furuya
metal co., ltd., Japan, and Lonmin PLC, UK.

REFERENCES
1
Green, M. L., Gross, M. E., Papa, L. E., Schnoes, K. J. and Brasen, D.," Chemical Vapor
Deposition of Ruthenium and Ruthenium Dioxide Films" J. Electrochem. Soc, 132, 2677-
2684(1985).
2
So, F. C. T., Kolawa, E., Zhao, X. -A., Pan, E. T. -S. and. Nicolet, M. -A., "Reactively
sputtered Ru0 2 and Mo-0 diffusion barriers",/ Vac. Sei. Technol, B5 , 1748-1749(1987).
3
Kolawa, E., So, F. C. T., Pan, E. T. -S. and Nicolet, M. -A., " Reactively sputtered Ru02
diffusion barriers", Appl. Phys. Lett., 50, 854-855(1987).
4
Rand, M. J.," Plasma-promoted deposition of thin inorganic films", J. Electrochem. Soc, 16,
420-427(1979).
5
Zhen, W., Vargas, R., Goto, T., Someno, Y. and Hirai, T." Preparation of epitaxial A1N films
by electron cyclotron resonance plasma-assisted chemical vapor deposition on Ir- and Pt-coated
sapphire substrates", Appl. Phys. Lett., 64, 1359-1361(1994).
6
Goto, T., Ono, T. and Hirai, T., "Electrochemical Properties of Amorphous Carbon/Nano-
granular Iridium Films Prepared by MOCVD", J. Jpn. Soc. Powder and powder Metallurgy, 47,
386-390(2000).
7
Irvine, J. T. S., Sinclair, D. C. and West, A. R., " Electroceramics: Characterization by
Impedance Spectroscopy", Adv. Mater., 2 , 132-138(1990).
8
Badwal, S. P. S. and Bruin, H. J. de, " Electrode Kinetics at the Pt/Yttria-Stabilized Zirconia
Interface by Complex Impedance Dispersion Analysis", Phys. Stat. Sol., (a)54,261-270(1979).

Novel Processing of Ceramics and Composites • 19

 Novel Processing of Ceramics and Composites
Edited by Narottam P. Bansal, J. P. Singh, James E. Smay and Tatsuki Ohji
Copyright © 2006 The American Ceramics Society

Combustion Synthesis
 Novel Processing of Ceramics and Composites
Edited by Narottam P. Bansal, J. P. Singh, James E. Smay and Tatsuki Ohji
Copyright © 2006 The American Ceramics Society

SYNTHESIS OF Sitio 5Sr0 5Co03.x AND Lao 6Sr0 4Co03-x NANOPOWDERS BY SOLUTION
COMBUSTION PROCESS

Narottam P. Bansal
National Aeronautics and Space Administration
Glenn Research Center
Cleveland, OH 44135

Zhimin Zhong
QSS Group, Inc.
NASA Glenn Research Center Group
Cleveland, OH 44135

ABSTRACT
Nanopowders of Smo.sSro.sCoOs-x (SSC) and Lao 6Sr0 4Co03.x (LSC) compositions, which
are being investigated as cathode materials for intermediate temperature solid oxide fuel cells,
were synthesized by a solution-combustion method using metal nitrates and glycine as fuel.
Development of crystalline phases in the as-synthesized powders after heat treatments at various
temperatures was monitored by x-ray diffraction. Perovskite phase in LSC formed more readily
than in SSC. Single phase perovskites were obtained after heat treatment of the combustion
synthesized LSC and SSC powders at 1000 °C and 1200 °C, respectively. The as-synthesized
powders had an average particle size of -12 nm as determined from x-ray line broadening
analysis using the Scherrer equation. Average grain size of the powders increased with increase
in calcination temperature. Morphological analysis of the powders calcined at various
temperatures was done by scanning electron microscopy.

1. INTRODUCTION
Solid oxide fuel cells (SOFC) are being considered1 as the premium power generation
devices in the future as they have demonstrated high energy conversion efficiency, high power
density, extremely low pollution, in addition to flexibility in using hydrocarbon fuel. A major
obstacle for commercial applications of SOFC still is high cost, both in terms of materials and
processing. Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) operated between
500~800°C, which allows utilization of available and inexpensive interconnects and sealing
materials, can significantly reduce the cost of SOFC. The IT-SOFC also will have better
reliability and portability. To keep up with the performance of traditional SOFC that operates
between 900-1000°C, new materials with improved performance have to be used2'3. To enhance
the oxygen ion conductivity of the electrolyte at the reduced temperature, Lai.xSrxGai.yMgyOz
(LSGM), scandium stabilized zirconia or lanthanum (gadolinium, samarium) doped ceria can be
used to replace the yttrium stabilized zirconia. Similarly, cathode materials with higher
performance at the lower temperature such as Smo.5Sro.5Co03.x (SSC), Lao.6Sr0.4Co03_x (LSC),
Lao gSr0 2Coo.2Feo.803.x (LSCF) will be used to substitute La^ySryMnOs.x (LSM), the performance
of which decreases rapidly when the operating temperature is below 800°C.
The primary objective of this study was to synthesize fine powders of SSC and LSC
compositions for applications as SOFC cathodes. A number of approaches such as, solid state
reaction, sol-gel, hydrothermal, spray-drying, freeze-drying, co-precipitation, and solution

23
Synthesis of Sm0 5Sr0 5Co03_x and La0.6Sr0 4Co03_x Nanopowders by Solution Combustion

combustion have been used for ceramic powders processing. The solution-combustion method is
particularly useful in the production of ultrafine ceramic powders of complex oxide compositions
in a relatively short time. This approach has been utilized4"10 for the synthesis of various oxide
powders such as ferrites, chromites, manganites, Ni-YSZ cermet, zirconates, doped ceria, hexa-
aluminates, pyrochlores, oxide phosphors, spinels, etc. An amino acid such as glycine is
commonly used as the fuel in the combustion process. However, urea, citric acid,
oxylydihydrazide, and sucrose have also been recently utilized6-10 as complexing agents and fuel
in the combustion synthesis.
In the present study, SSC and LSC cathode powders were synthesized using the glycine-
nitrate solution-combustion technique4"6 because of its high energy efficiency, fast heating rates,
short reaction times, and high reaction temperatures. This process is also unique as all the
reactants are mixed in solution at the molecular level resulting in homogeneous reaction products
and faster reaction rates. Development of crystalline phases in the powders, on heat treatments at
various temperatures, was followed by powder x-ray diffraction. Morphology of the powders
was characterized by scanning electron microscopy (SEM).

2. EXPERIMENTAL METHODS

2.1. Powder Synthesis:

The starting materials used in the synthesis were metal nitrates Sm(N03)3.6H20 (99.9 %
purity), La(N03)3.6H20 (99.9% purity), Sr(N03)2 (98 % purity), Co(N03)2.6H20 (97.7 %
purity) and glycine (NH2CH2COOH, 99.5 % purity), all from Alfa Aesar. A flow chart showing
the various steps involved in the synthesis of powders by the solution-combustion process is
shown in Fig. 1. Metal nitrates are employed both as metal precursors and oxidizing agents.
Stoichiometric amounts of the metal nitrates, to yield 10g of the final SSC or LSC oxide powder,
were dissolved in deionized water. A calculated amount of the amino acid glycine (0.7 mole per
mole of NO3") was also dissolved in deionized water. The glycine solution was slowly added to
the metal nitrate aqueous solution under constant stirring. Glycine acts as a complexing agent for
metal cations of varying sizes as it has a carboxylic group at one end and an amino group at the
other end. The complexation process increases the solubility of metal ions and helps to maintain
homogeneity by preventing their selective precipitation. The resulting clear and transparent red
colored solution was heated on a hot plate until concentrated to about 2 mole/liter on metal
nitrate basis. While the solution was still hot, it was added drop wise to a 2 liter glass beaker that
was preheated between 300~400°C. The water in the solution quickly evaporated, the resulting
viscous liquid swelled, auto-ignited and initiated a highly exothermic self-contained combustion
process, converting the precursor materials into fine powder of the complex oxides. Glycine acts
as a fuel during the combustion reaction, being oxidized by the nitrate ions. Oxygen from air
does not play an important role during the combustion process. The overall combustion reactions
can be represented as:

0.6 La(N03)3 + 0.4 Sr(N03)2 + Co(N03)2 + 3.2 H2NCH2COOH + (1.8 - x/2) 0 2 —

Lao 6Sr0 4Co03.x + 6.4 C0 2 + 8 H 2 0 + 3.9 N2 (1)

0.5 Sm(N03)3 + 0.5 Sr(N03)2 + Co(N03)2 + 3.2 H2NCH2COOH + (1.95 - x/2) 0 2 -+

Smo5Sro5Co03.x + 6.4 C0 2 + 8 H 2 0 + 3.85 N2 (2)

24 • Novel Processing of Ceramics and Composites

 Synthesis of Sm06Sr05Co03_x and La0.6Sr0 ^CoCv,, Nanopowders by Solution Combustion

Nitrates of La, Sm, Glycine + water

Sr, Co + water

Mix metal nitrates and

glycine solutions
under stirring

G
Clear red solution; heat at -80 °C;
concentrate to ~2M metal nitrate basis
D
Add above solution dropwise to a
beaker preheated to 300-400 °C

Black powder; heat treat

700-1300 °C, 2 h each,
in air

I
f XRD, SEM )

Figure 1 —Flow chart for solution-combustion synthesis

of Lan.eSrn 4CoC>3.x and Smrj.sSrn 5CoC>3-x nano-
powders

indicating the formation of CO2, N2, and H2O as the gaseous products. The evolution of gases
during the combustion process helps in the formation of fine ceramic powder by limiting the
inter-particle contact. The resulting black powder contained some carbon residue and was further
calcined to convert to the desired product. Small portions (~1 g) of this powder were heat treated
in air at various temperatures between 700 and 1300°C for two hours to study the development of
crystalline phases.

2. 2. Characterization
Thermal gravimetric analysis (TGA) of the powders was carried out using a Perkin-
Elmer Thermogravimetric Analyzer 7 system which was interfaced with computerized data
acquisition and analysis system at a heating rate of 10 °C/min. Air at 40 ml/min was used as a
purge gas. X-ray diffraction (XRD) analysis was carried out on powders heat treated at various
temperatures for crystalline phase identification and crystallite size determination. Powder XRD
patterns were recorded at room temperature using a step scan procedure (0.02720 step, time per
step 0.5 or 1 s) in the 20 range 10-70" on a Philips ADP-3600 automated diffractometer equipped
with a crystal monochromator employing Cu K„ radiation. Microstructural analysis was carried
out using a JEOL JSM-840A scanning electron microscope (SEM). Prior to analysis, a thin layer
of Pt or carbon was evaporated onto the SEM specimens for electrical conductivity.

Novel Processing of Ceramics and Composites • 25

Synthesis of Smo.5Sr05Co03_x and Lao.eSro.iCoCvx Nanopowders by Solution Combustion

3. RESULTS AND DISCUSSION

3.1. Thermogravimetric Analysis

Figure 2 shows the TGA curves recorded at a heating rate of 10'C/min in air from room
temperature to 1200°C for the as-synthesized LSC and SSC powders using the solution-
combustion method. For both precursors, about 6% weight loss was observed between 600 to
850°C that was likely due to loss of carbon residue by oxidation and also from decomposition of
SrCOi. For SSC, there was additional 1% weight loss between 850 to 1000°C for which there is
no simple explanation based on the x-ray diffraction results of Figure 4.

102

100
c
o
I 98
8
S> 96
I
1 94
O)
to
I 92
Q.
90

88
0 200 400 600 800 1000 1200
Temperature, "C
Figure 2—TGA curves of as-synthesized precursor powders by solution-
combustion method for Lao 6Sro.4Co03_x and Smo.sSro.sCoOs.,, at a
heating rate of 10 °C/min in air.

3.2. Phase Formation and Microstructure

Both the LSC and SSC as-synthesized powders were calcined in air for two hours at
various temperatures between 700 to 1300 °C to investigate the evolution of crystalline phases.
X-ray diffraction patterns for these heat treated LSC and SSC powders are shown in Figs. 3 and
4, respectively and the results are summarized in Table I. The as-prepared LSC powder shows
weak crystallinity of the perovskite phase. SrCOj phase was also observed in the as-synthesized
powder and after calcination at 700 °C. An unknown peak at 32° (probably Sr3Co2Û6 13, 83-375)
appeared for the powder calcined at 800 and 900 °C. Formation of the perovskite phase,
Lao.6Sro4Co03.x, is completed above 1000°C as observed by XRD results in Fig. 3. The as-
prepared SSC powder showed the presence of S1ÏI2O3, C03O4, and SrC03 phases. The desired
Smo.jSro.5Co03.x perovskite phase emerged as the major phase after the powder was calcined at

26 • Novel Processing of Ceramics and Composites

Synthesis of Sm 0 5Sr0 5 Co0 3 _ x and La0 6Sr0 4Co03_x Nanopowders by Solution Combustion

Figure 3.—X-ray diffraction patterns of Lao.6Srrj 4C0O3-X

powders made by solution-combustion synthesis after heat
treatments at various temperatures for 2 h in air.

Figure 4.—X-ray diffraction patterns of Smo.5Srrj.5Co03-x

powders made by solution-combustion synthesis after heat
treatments at various temperatures for 2 h in air.

Novel Processing of Ceramics and Composites • 27

Synthesis of Sm0.5Sr0.5CoO3_x and La0.6Sr0.4CoO3_x Nanopowders by Solution Combustion

700 °C. Secondary phases such as Sr3Co20613 remained even after the powder was heat treated at
1100 °C. Perovskite phase-pure Smo.sSro sCo03_x powder was obtained after heat treatment at
1200° C for 2 hours. Earlier investigation7 of SSC synthesis by solid-state reaction method
indicated that the perovskite phase was formed after calcination at 1200°C for 6 hours. The
products calcined at this temperature will have low porosity and non-ideal microstructure as
cathode materials.

Table. I. X-ray diffraction analysis of Sm0 5Sr0 5C0O3., and Lao éSr0 4Co03.x powders made by
solution-combustion synthesis after heat treatments at various temperatures in air

System Heat treatment Crystalline phases" Average

Temp. Time grain size
CC) (h) (nm)b
Lao 6 Sr 0 4 Co0 3 . x As Lao. 6 Sr 04 Co0 3 . x , SrCOj 12
synthesized
700 2 Lao 6 Sr 0 4 Co0 3 . x , SrCCB 15
800 2 Lao óSro 4 Co0 3 _ x , low intensity peak at 32" 28 17
900 2 Lao iSro 4 Co0 3 . x , low intensity peak at 32' 28 28
1000 2 Lao óSro 4 Co0 3 . x 37
1100 2 Lao6Sro4Co0 3 . x 50
1200 2 Lao6Sro4Co03_x
1300 2 Lao6Sr 0 4Co0 3 - x
m0 5 Sr 0 sCo0 3 . x As — Sm 2 0 3 , Co 3 0 4 , SrC0 3 —
synthesized
700 2 Smo 5 Sr 0 5 Co0 3 . x , SrC0 3 , Co 3 0 4 15
800 2 Sm 0 5 Sr 0 5 Co0 3 _ x , Sr 3 Co 2 0 6 , 3 , Co 3 0 4 15
900 2 Sm0 sSr0 sCo0 3 . x , Sr3Co20613 25
1000 2 Sm 0 sSr0 sCo0 3 . x , Sr3Co20,s l3 low intensity 38
peak at 32" 28
1100 2 Smo sSro sCo0 3 . x , Sr 3 Co 2 0 6 , 3 low intensity 41
peak at 32° 26
1200 2 Smo5Sr 05 Co0 3 . x
1300 2 Sm 0 5Sro5Co0 3 . x
"Phases in decreasing order of peak intensity
b
Calculated from Scherrer formula using FWHM of XRD peak in 47-48° range of 29.

The SEM micrographs of Lao óSro 4Co03.x and Smo 5Sr0 5Co03.x powders made by
solution-combustion synthesis after heat treatments at different temperatures for 2 h in air are
presented in Figures 5 and 6, respectively. The as prepared powders were highly porous and
particles were linked together in agglomerates of different shapes and sizes. Substantial particle
growth was observed upon calcination for two hours at 1000°C or higher temperatures. The
particle size of samples calcined at 1000°C increased but the structure remained highly porous,
which resembled the typical cathode structure for SOFC. Therefore, LSC and SSC powders

28 • Novel Processing of Ceramics and Composites

 Synthesis of Smo.5Sro.5Co03_x and La06Sr0 ^CoO^,, Nanopowders by Solution Combustion

should be sintered around 1000"C for fabrication of cathode structures. After calcination at
1200°C. LSC became dense and lost porosity. SSC powder sintered into a dense pellet following
heat treatment at 1200°C.

Figure 5.—SEM micrographs of Lao.6Sro.4Co03_x powders made by solution-combustion synthesis after heat
treatments at different temperatures for 2 h in air.

3.3. Particle Size Analysis

After each heat treatment of the as synthesized LSC and SSC powders, the average
particle size was evaluated from X-ray line broadening analysis using the Scherrer equation":

t = 0.9 X/(B cos 9B) (3)

where t is the average particle size, X the wave length of Cu K<, radiation, B is the width (in
radian) of the XRD diffraction peak at half its maximum intensity, and OB the Bragg diffraction
angle of the line. Correction for the line broadening by the instrument was applied using a large
particle size silicon standard and the relationship

Novel Processing of Ceramics and Composites • 29

Synthesis of Sm0 5Sr0 5Co03_x and La0 6Sr0 4Co03_x Nanopowders by Solution Combustion

B2 = B2M - B2s (4)

where BM and B s are the measured widths, at half maximum intensity, of the lines from the
sample and the standard, respectively. Values of average grain sizes of the as synthesized SSC
and LSC powders and of those after heat treatments at various temperatures are given in Table I.

Figure 6—SEM micrographs of Smn.sSro 5C0O3.X powders made by solution-combustion synthesis after heat
treatments at different temperatures for 2 h in air,

The as synthesized powders had an average grain size of about 10-12 nm. A number of factors
are responsible for the nanosize of the resulting powders. Before the reaction, all the reactants
are uniformly mixed in solution at atomic or molecular level. So, during combustion, the
nucleation process can occur through the rearrangement and short-distance diffusion of nearby
atoms and molecules. Also, large volume of the gases evolved during the combustion reactions
(1) and (2) limits the inter-particle contact. Moreover, the combustion process occurs at such a

30 • Novel Processing of Ceramics and Composites

 Synthesis of Sm0 5Sr0 5Co03_x and La0 6Sr0 ^CoO^* Nanopowders by Solution Combustion

fast rate that sufficient energy and time are not available for long-distance diffusion or migration
of the atoms or molecules which would result in growth of crystallites. Consequently, the initial
nanosize of the powders is retained after the combustion reaction.
The X-ray line broadening method can be used only for the size determination of small
crystallites (< 100 nm). The values obtained are not the true particle size, but the average size of
coherently diffracting domains; the latter being usually much smaller than the actual size of the
particles. The crystallite size of the as-synthesized powder depends8'9 on the glycine to nitrate
ratio used during the combustion synthesis. Powder made using a fuel-deficient system has the
highest surface area. The powder surface area decreases as the glycine to nitrate ratio is
increased. This has been attributed to an increase in the flame temperature during combustion
which helps in the growth of crystal size. The average grain size of the SSC and LSC powders
increased (Table I) with the increase in calcination temperature, as expected.

4. SUMMARY AND CONCLUSIONS

Nanopowders of Smo.sSro 5C0O3.X (SSC) and Lao.öSro 4Co03.x (LSC) cathode materials
for solid oxide fuel cells have been synthesized by the glycine-nitrate solution-combustion
method. Formation of crystalline phases in both the powders started at relatively low
temperatures. However, the as-synthesized powders had to be calcined at or above 1000 °C to
yield phase pure perovskite products. The high temperature calcination caused significant
reduction in surface area, coarsening of the powders, and sintering which is not favorable for
forming the cathode structures for SOFC. The investigations of electrochemical activity of these
materials and co-sintering with fuel cell electrolytes are being investigated and will be presented
in the future.

ACKNOWLEDGMENTS
Thanks are due to Ralph Garlick for X-ray diffraction analysis. This work was supported
by Low Emissions Alternative Power (LEAP) Project of the Vehicle Systems Program at NASA
Glenn Research Center.

REFERENCES
1. N. Q. Minh, Ceramic Fuel Cells, J. Am. Ceram. Soc., 76_[3], 563-588 (1993).
2. D. Stover, H.P. Buchkremer, S. Uhlenbruck, Processing and Properties of the Ceramic
Conductive Multilayer Device SOFC, Ceram. Int., 30 [7], 1107-1113 (2004).
3. Y. Liu, S. Zha, M. Liu, Adv. Mater., 16 [3], 256-260 (2004).
4. S.-J. Kim, W. Lee, W.-J. Lee, S. D. Park, J. S. Song, and E. G. Lee, Preparation of
Nanocrystalline Nickel Oxide-Yttria-Stabilized Zirconia Composite Powder by Solution
Combustion with Ignition of Glycine Fuel, J. Mater. Res., 16 [12], 3621-3627 (2001).
5. L. A. Chick, L. R. Pederson, G. D. Maupin, J. L. Bates, L. E. Thomas, and G. J. Exarhos,
Glycine-Nitrate Combustion Synthesis of Oxide Ceramic Powders, Mater. Lett., 10, 6-12
(1990).
6. M. Marinsek, K. Zupan, and J. Maeek, Ni-YSZ Cermet Anodes Prepared by Citrate/Nitrate
Combustion Synthesis, J. Power Sources, 106, 178-188 (2002).
7. T. Ishihara, M. Honda, T. Shibayama, H. Minami, H. Nishiguchi, Y. Takita, Intermediate
Temperature SOFCs Using a New LaGaÛ3 Based Oxide Ion Conductor. I. Doped SmCo03
as a New Cathode Material, J. Electrochem. Soc, 145 [9], 3177-3183(1998).

Novel Processing of Ceramics and Composites • 31

Synthesis of Sm 0 5Sr0 5Co03_x and La0 6Sr0 4CoC>3_x Nanopowders by Solution Combustion

8. R. D. Purohit, S. Saha, and A. K. Tyagi, Nanocrystalline Thoria Powders via Glycine-

Nitrate Combustion, J. Nuclear Mater., 288 [1], 7-10 (2001).
9. T. Ye, Z. Guiwen, Z. Weiping, and X. Shangda, Combustion Synthesis and
Photoluminescence of Nanocrystalline Y2O3: Eu Phosphors, Mater. Res. Bull., 32, 501
(1997).
10. K. Prabhakaran, J. Joseph, N. M. Gokhale, S. C. Sharma, and R. Lai, Sucrose Combustion
Synthesis of LaxSr(i.x)Mn03 (x < 0.2) Powders, Ceram. Int., 31 [2], 327-331 (2005).
11. B. D. Cullity, Elements ofX-Ray Diffraction, T* Edition, Addison-Wesley, Reading, MA, p.
284(1978).

32 • Novel Processing of Ceramics and Composites

 Novel Processing of Ceramics and Composites
Edited by Narottam P. Bansal, J. P. Singh, James E. Smay and Tatsuki Ohji
Copyright © 2006 The American Ceramics Society

CHEMISTRY PURIFICATION OF TITANIUM DIBORIDE POWDER SYNTHESISED BY

COMBUSTION SYNTHESIS PROCESSES

Wang Weimin* Fu Zhengyi Wang Hao

State Key Lab of Advanced Technology for Materials Synthesis and Processing,
Wuhan University of Technology
Wuhan 430070, P.R.China

ABSTRACT:
Combustion synthesis method with reductive process was used to synthesize TÍB2 powder from
TÍO2 — B2O3 — Mg system. Main impurity phase can be cleaned out by acid washing treatment.
The influences of acid washing conditions (acid concentration, treatment time, treatment
temperature and so on) on the purity of TÍB2 powder were studied. Results showed that acid
treatment temperature and amount of excessive acid were the main factors that effected purity of
TiB2 powder. With increase of acid treatment temperature and amount of excessive acid, purity
of TiB2 powder increased continuously. The analysis of thermodynamics and kinetics showed
that the increase of acid treatment temperature could increase chemistry reaction speed constant
(K), and accelerate acid washing processing. Diffusion mechanism controlled mainly acid
treatment reaction.

1. INTRODUCTION
TiB2 Ceramic has excellent physcc—chemical properties such as high melting point, high
hardness, good corrosion resistance and high temperature mechanical properties, TiB2 ceramic
has also an excellent electricity conductivity, which make TÍB2 materials have a wide application
areas as advanced engineering ceramicsl1'2'. Traditional fabrication methods of TiB2 ceramic
powder such as carbon -thermal reduce processing need a longer thermal treatment time and
consume a great deal of energy, and however, this technology could not produce the TÍB2
powder with high purity, small particle size and lower price.

Combustion Synthesis technology is a novel materials synthesis and processing technology

which is receiving more and more interests in recent decades because of the following
advantages: simple processes, less energy consume, high production efficiency and so on '3'.
Combustion Synthesis method has been employed to synthesise TÍB2 ceramic powder from
element Boron and Titanium '4|, but due to the high cost of element boron and titanium, the
commercial production of TÍB2 ceramic is impossible by this method. Combustion Synthesis of
TÍB2 ceramic powder from various oxides such as Boron Oxide and Titanium Oxide is a possible
way to obtain TÍB2 ceramic with low costing and high purity'5'. In this processing, one of the key
steps is the acid washing treatment to clean away impurity , which decide the final purity of TiB2
ceramic powder.

In this paper, acid washing conditions effect the purity of TiB2 powder were studied, the
thermodynamics and kinetics of acid washing processing were discussed.

Corresponding author: State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of
Technology, Wuhan 430070, P. R. China, Fax: 00862787879468, E-mail: wangwm@hotmail.com

33
Chemistry Purification of Titanium Diboride Powder Synthesised by Combustion Synthesis

2. EXPERIMENTAL
The raw materials used in this paper were Mg powder, TÍO2 and B2O3 powder. Powder
characteristics were shown in Table 1.

TÍB2 powder can be synthesized according to following chemistry reaction:

Ti0 2 + B2O3 +5 Mg = TiB2+ 5MgO (1)

The main impurity in TÍB2 powder is MgO, which can be cleaned away by acid washing .The
raw powders were mechanically mixed in dry condition after weighing .The mixture powder
were axially compacted into cylinders, and then was putted into combustion synthesis chamber.
Synthesis temperature and synthesis processing were monitored by means of an infrared
thermometer and high—speed video camera, respectively. The ignition head is a tungsten coil,
which can provide an ignition temperature in the range of 2000--3000 K by the changing the
voltage. Specimens were synthesised in an argon atmosphere.

After combustion synthesis, the synthesized production was ball milled for 1 hour. Ball milled
fine powder was soaked in hydrochloric acid solution. After a certain time of soaking, the
powder was cleaned using distilled water a few times, after that, filtering and vacuum-dry
processing were followed. X-ray diffraction quantitative analysis method was used to measure
the residual MgO content in TÍB2 powder. Scanning electronic microscopy was employed to
reveal the microstructure of powder.

3. RESULTS AND DISCUSSION

3.1 Influence of combustion synthesis parameters on the mineral phase component of synthesized
sample
Literature[6) showed that combustion synthesis parameters such as density of sample, synthesis
pressure, and diluent have great influences on processing characteristics of combustion synthesis
and component of synthesized sample. Literature [7' showed that synthesized production
consisting of only TÍB2 and MgO cannot be obtained according to the standard stoichiometric
(Ti02: B203: Mg = 1:1:5), but the suitable component of reactant mixture have not been
suggested.

From analysis of combustion synthesis processes of this reaction system, the synthesis reaction
consists of two steps. Firstly, metal Mg reduced B2O3 and TÍO2 to form element B and Ti,
secondly, TÍB2 was synthesized by chemical combination of two monomer element. Obviously,
in these reducing processes, the reduced degree of oxides has a direct influence on the mineral
phase composition of synthesised product, metal Mg play an important role in controlling the
reduced degree and phase composition. Study showed that when reducer Mg is not enough for
oxides, 3MgO B2O3 appears in synthesised production according to following chemistry reaction:

3MgO+B203=3MgO B2O3 (2)

Fig.l. showed the influence of amount of Mg in reactant mixture on content of 3MgOB203 in

synthesised sample. With increase of the Mg content, the content of 3MgO B2O3 decreased

34 • Novel Processing of Ceramics and Composites

 Chemistry Purification of Titanium Diboride Powder Synthesised by Combustion Synthesis

remarkably, when the TÍO2: B2Û3: Mg is equal to 1:1:7, 3MgO B2O3 almost could not been
detected. Figure 2 showed the X-ray diffraction result, the diffraction peak intensity of 3MgO
B2O3 is very low.

3.2 Effects of acid washing conditions on the purity of TÍB2 powder

Influences of acid concentration and amount of excessive acid on the residual MgO content in
TÍB2 powder were shown in Fig.3. It can be found from Fig.3.a that under the same treatment
temperature and time, the residual MgO content decreased with increase of acid concentration.
This indicated that increased acid concentration was helpful to clean out MgO. When the acid
concentration is 2M, the residual MgO content is less than 20wt%, but further increase of acid
concentration seem to have no obvious influence on the residual MgO content. When acid
concentration is fixed, the increase of amount of excessive acid resulted in the decrease of
residual MgO content (Fig3.b). When the amount of excessive acid surpassed 50vol%, the
residual MgO content in TÍB2 powder did not decrease obviously with continuous increase of
amount of excessive acid.

The results showed in Fig.3 indicated that it is impossible to get high pure TiB2 powder at room
temperature. In order to obtain TÍB2 powder with high purity, it is necessary to increase acid
washing temperature and time.

Fig.4 showed the influence of acid washing temperature and time on residual MgO content in
TÍB2 powder. From Fig.4.a, it can be seen that the residual MgO content decreased with increase
of acid washing time. At room temperature (298K), when acid treatment time was more than
15hrs, the residual MgO content seems to no longer decrease, and the residual MgO content is
about 15—18wt%, however, when acid washing temperature was raised to 333K, residual MgO
content will decrease continuously and quickly with increase of acid washing time. MgO content
in TiB2 powder can be respectively decreased to less than 8wt% and 2wt% after acid washing 2
and 5 hours. Increase of acid washing temperature can accelerate remarkably the acid washing
processing, and shorten acid time, which have been proved also by experiment results shown in
Fig.4b. Certainly, too high acid washing temperature is not better, which cause the increasing of
residual MgO content due to volatilization of hydrochloric acid at high temperature.

Scanning electronic microscopy was employed to observe the microstructure of TÍB2 powder.
Fig .5 showed the morphology of pure TÍB2 powder, which is fine, uniform and agglomerate -
free.

3.3 DISCUSSION
3.31. The thermodynamics analysis
In the combustion synthesis of TÍO2 ~ B2O3 — Mg system, the synthesized powder consists of
MgO and TÍB2. During acid washing, the MgO was cleaned out and TiB2 did not take part in any
chemistry reaction, the chemistry reaction of acid washing processing can be expressed by
following reaction equation:

MgO(s) + 2H+ =Mg 2 + + H 2 0 (3)

Novel Processing of Ceramics and Composites • 35

Chemistry Purification of Titanium Diboride Powder Synthesised by Combustion Synthesis

The free energy change of acid washing reaction AG"2i)8 can be written as following:

AG°298 = (AG° Ms 2++ AG°H2 o) - (AG°Mgo + AG°H2+) (4)

According to equation (4), the free energy change of acid washing reaction at room temperature
can be calculated, the calculation value is AG°29g = -122.58KJ, which is less than zero and
indicates this chemistry reaction can initiate automatically at room temperature.

When temperature of reaction system was increased, the system free energy changeAG"T will
change. According to G.R. Kirchhoff principle, system free energy changes at different
temperature can be calculated by equation (5)

AG°T = A G ° 2 9 8 - TAS°2,8 +J"^ 8 ACpdT -T J ^ ACpd(lnT) (5)

AS°298 is the change of standard entropy, ACp is average thermal capacity. When reaction
temperature is 333K (60 °C), the system free energy changes AG" 333= -120.6kJ < 0, which is
less than that of room temperature, showing the acid washing reaction is exothermal reaction.
Chemistry reaction activation energy can be calculated according to the relationship between
reaction free energy change and activation energy. At room temperature T = 298 K. the
calculated reaction activation energy E = 83.68 kJ/mol.

Chemistry reaction rate constant K is a function of temperature, increasing of temperature will

cause change of reaction rate constant. According to Van't Hof theorem, chemistry reaction rate
constant at different reaction temperature KT can be calculated:

In (KT+iT /KT) = EAT/(R T) (6)

Where, E is the activation energy, R is gas constant and T is temperature. If reaction temperature
increase 10 K, the KT+IO /KT is about 2.7, which means thelO K increasing of reaction
temperature will cause about 2.7 times increasing of reaction rate constant, chemistry reaction
will also be accelerated significantly. The experimental results agreed well with this calculated
result.

3.3.2. The kinetics analysis

Acid washing treatment is a solid/liquid reaction process. During acid washing, mass transfer
and chemistry reaction take place according to following steps: Transfer of reactant W to solid
surface ( MgO) — Adsorption of reactant H+on solid surface ( MgO) — Chemistry reaction on
solid surface (MgO) — Separation of reaction production from solid surface (MgO) — Transfer
of reaction production to solution. In this multiphase reaction system, the speed of acid washing
depends on the slowest steps in acid washing process. In HC1 — MgO reaction system,
adsorption and separation is quicker, chemistry reaction MgO + H+ = Mg2+ + H 2 0 is also quicker,
the diffusion step is the slowest. Diffusion processes determined the speed of acid washing
processing.

36 • Novel Processing of Ceramics and Composites

 Chemistry Purification of Titanium Diboride Powder Synthesised by Combustion Synthesis

When H ion diffuse to MgO solid surface, a liquid state diffusion layer with a concentration
gradation was formed. H + ion diffuses to MgO solid surface through diffusion layer, and takes
part in chemistry reaction continuously. The diffusion equation can be written as following:

dn/dt - DS(dc/dx) (7)

Where, D is diffusion coefficient, S is surface area of solid particle, dc/dx is concentration

gradation. Concentration of hydrochloric acid on the MgO surface is almost zero due to quick
solid/liquid chemistry reaction, and the concentration of outside of diffusion layer is about
concentration of hydrochloric acid solution C. So that the diffusion equation can be changed to:

dn/dt = DSC/A. (8)

X is thickness of diffusion layer. Equation (8) showed chemistry reaction speed has a direct
proportion with concentration of hydrochloric acid solution C, increasing of hydrochloric acid
concentration will accelerate acid washing speed, which have been proved by our experiments.
When we suppose MgO particles were uniform distribution in hydrochloric acid solution and the
MgO solid particle is a ball with a radius ro? the relationship between the chemistry reaction
degree of MgO solid particle and acid washing time can be expressed as following:

r0/M

Where, M and p are respectively molecular weight of MgO and density. Equation (9) showed
that the longer the acid washing time , the higher the reaction degree a , and the lower the
residual MgO content in TÍB2. This agrees with experiment results. However, in the combustion
synthesis production, some T1B2 particle and MgO particle cohere each other, and even MgO
particle was coated by TÍB2 particle. Hence, only prolongation of acid washing time could not
clean out residual MgO completely.

4. CONCLUSION
From above experiment study and analysis, following conclusion can be summarised:
(1) In combustion synthesis processes, Mg plays an important role in controlling the mineral
phase component of synthesised product. When the TÍO2 : B2O3 : Mg is proper, there is almost
no impurity to be detected in synthesised powder. After acid washing treatment, pure TÍB2
powder can be obtained.
(2) In acid washing processes, residual MgO content in TÍB2 powder depends on acid
concentration, amount of excessive acid, treatment times, and treatment temperature. With
increasing of acid concentration, amount of excessive acid, treatment time, residual MgO content
decreased gradually, increase of acid washing temperature accelerated acid washing speed
remarkably.
(3) Thermodynamics analysis showed that acid washing processes can carry out automatically
at room temperature but longer treatment time is needed. Increase of acid washing temperature
can quicken this process.
(4) Kinetics analysis showed that acid washing process is controlled by diffusion mechanism.

Novel Processing of Ceramics and Composites • 37

Chemistry Purification of Titanium Diboride Powder Synthesised by Combustion Synthesis

ACKNOWLEDGEMENTS
The authors are grateful to the project of National Hi-Tech Research and Develop of China for
this work under Grant number: 2001AA333020

REFERENCE
[1] Rieded Ralf(Ed.),Handbook of Ceramic Hard Materials, Weinheim: Weily-VCH,2000
[2] J.Matsushita, T.Suzuki, A.Sano, Wire Electronical Discharge Machining of TiB2 composites,
J. Ceram. Soc. Jap., Vol 100(1992),219-222
[3] R. W.Rice, W.R.Grance and C.Conn, Reactant compact and product microstructure for TiC,
TiB2 and TiC/ TiB2 from SPS processing, Ceram. Eng. Sei and Proce, Voll 1, pi 192, pi990-1203
[4] V.I.Yukhvid, Modifications of SHS Processes, Pure and Applied Chemistry, Vol64(7), p977-
988,1992
[5]Wang Weimin, Fu Zhengyi, Wang Hao, Chemistry Reaction Processes During Combustion
Synthesis of B2O3—Ti02—Mg System, Journal of Materials Processing and Technology, Vol ()
2002.
[6] Pampuch R , Some Fundamental Versus Practical Aspects of Self-propagating High-
temperature Synthesis, Solid State Ionics, Vol 101(NOV),p 899-907,1997
[7] A.G.Merzhanove, Combustion processes that synthesize materials, J. of Mate. Proce. Tech,
Vol 56 , p222, 1996

Table 1 Characteristics of the raw materials powders

Raw materials Purity (%) Main impurity Average particle size (p.m)
Mg 98 Si Al Fe 70
Ti02 99 Fe 2 0 3 , Sn0 2 1
B203 97 S i 0 2 , Al 2 0 3 70

38 ■ Novel Processing of Ceramics and Composites

Chemistry Purification of Titanium Diboride Powder Synthesised by Combustion Synthesis

Fig. 1. Influence of amount of Mg in reactant mixture on the content of 3MgO B2O3 in

synthesised sample

Fig.2 .X-ray diffraction pattern of synthesised product when

Ti0 2 : B203; Mg (mole) is 1:1:7

Novel Processing of Ceramics and Composites • 39

Chemistry Purification of Titanium Diboride Powder Synthesised by Combustion Synthesis

Fig.3. Influences of acid concentration (a) and amount of excessive acid (b) on the residual MgO
content in T1B2 powder

40 • Novel Processing of Ceramics and Composites

 Another Random Document on
Scribd Without Any Related Topics
 2 cups all-purpose flour
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
¼ teaspoon salt
¼ teaspoon cloves
½ teaspoon nutmeg
1 teaspoon cinnamon
½ cup butter, or other shortening
1 cup sugar
1 egg
1 cup raisins, chopped
1 cup nutmeats, coarsely broken
1 cup thick apple sauce

1. Sift, then measure the flour. Sift three times with the baking soda,
salt and spice.

2. Cream the butter well. Gradually add sugar, beating after each
addition.

3. Add the egg, beating well, then the raisins and nuts.

4. Alternately add the dry ingredients and apple sauce, beating until
smooth after each addition.

5. Turn into a greased loaf pan. Bake.

Amount: 9 × 9 inch pan Temperature: 350° F. Time: 1 hour

15 minutes

CHOCOLATE NUT CAKE

1⅓ cups pastry flour
¾ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
 ⅓ cup butter, or other shortening
¾ cup sugar
1 egg
½ cup nutmeats, coarsely cut
2 ounces (2 squares) unsweetened chocolate
¾ cup sour milk or buttermilk
1 teaspoon vanilla

1. Sift, then measure flour. Sift again with the baking soda and salt.

2. Cream the butter until light and lemon colored. Add the sugar
gradually, beating after each addition.

3. Slowly add the egg which has been beaten until it is almost as
stiff as whipped cream.

4. Add the nutmeats, then the chocolate which has been melted and
cooled.

5. Combine the vanilla and sour milk. Alternately add the dry and
liquid ingredients, beating until smooth after each addition.

6. Turn into greased pan and bake in moderate oven.

Amount: 8 × 8 inch pan or a tube pan Temperature: 350° F.

Time: 40-45 minutes See page 17

16
 Frostings

ORANGE COCONUT FROSTING

3 tablespoons butter
2 cups confectioners sugar
¼ cup orange juice
¾ cup grated coconut

1. Cream butter until very soft.

2. Add sugar gradually, thinning with orange juice to spreading

consistency. Beat until smooth.

3. Beat coconut into frosting.

Amount: 1½ cups See page 8

FOAMY SAUCE
½ cup butter
1 cup confectioners sugar
2 egg yolks
 ¼ cup brandy
2 egg whites

1. Cream butter until light and lemon colored.

2. Gradually add sugar, beating until light and fluffy.

3. Add egg yolks, one at a time, beating until well blended.

4. Add brandy. Place in upper part of double boiler over simmering

water and cook until thickened, stirring constantly.

5. Pour slowly over egg whites which have been stiffly beaten. Blend
gently but thoroughly. Serve immediately.

Amount: 2 cups

MAPLE CREAM FROSTING

½ cup maple syrup
1 pound confectioners sugar
¼ cup butter, melted
¼ cup milk
Dash of salt

1. Heat maple syrup to boiling and cook 3 minutes.

2. Combine sugar, butter, milk and salt.

3. Add syrup and beat until light and thick.

4. This makes sufficient frosting to generously cover tops of two 9-

inch layers.
 BUTTER FROSTING
4 tablespoons butter
2 cups confectioners sugar
2 tablespoons milk
1 teaspoon vanilla

1. Cream butter until very soft.

2. Add sugar gradually, thinning with milk until it is of spreading

consistency.

3. Add vanilla. Beat until smooth.

Amount: 1 cup See page 8

17
 18

QUICK BUTTERSCOTCH FROSTING

2 tablespoons granulated sugar
¼ cup boiling water
2½ cups confectioners sugar
¼ cup milk
2 tablespoons butter

1. Make a caramel syrup of the granulated sugar by heating it slowly

over a flame until it melts and becomes straw colored. Remove
from fire. Add boiling water carefully as it spatters. Stir until sugar
is dissolved.

2. Cream butter until soft. Add ½ cup of confectioners sugar. Then

add sugar syrup, beating well. Add remaining confectioners sugar
gradually, thinning with milk to a spreading consistency.

FLUFFY FROSTING
1 cup sugar
2 egg whites
4 tablespoons cold water
¼ teaspoon cream of tartar
Dash of salt
½ teaspoon vanilla

1. Combine sugar, unbeaten egg whites, water, cream of tartar and

salt in upper part of double boiler.

2. Place over boiling water and beat constantly with rotary type
beater until frosting will stand in peaks, or about 7 minutes. Add
vanilla last.
 Amount: 3 cups See page 17

SOFT CHOCOLATE FROSTING

1 cup confectioners sugar
1 egg
Dash of salt
2 squares (2 ounces) unsweetened chocolate
½ teaspoon vanilla

1. Gradually add sugar to the slightly beaten egg. Beat until smooth
and light.

2. Add salt and melted chocolate, blending well. Add vanilla. Cool
before spreading.

3. This makes sufficient to cover tops and sides of an 8 × 8 inch loaf

cake.

LEMON FILLING
Juice and grated rind of 1 lemon
½ cup sugar
¾ cup water
2½ tablespoons cornstarch
2 tablespoons water
1 egg yolk

1. Combine lemon juice, rind, sugar and ¾ cup water. Slowly bring
this mixture to boiling point.
2. Make a smooth paste of cornstarch and the 2 tablespoons of
water. Add slowly to syrup, stirring constantly. Cook until mixture
is thick and clear, or about 5 minutes. Remove from heat.

3. Add small amount to slightly beaten egg yolk. Beat vigorously.

Return to remaining mixture and blend well. Cool.

Amount: 1½ cups See page 17

19
 Cookies

COCONUT ICEBOX COOKIES

4 cups all-purpose flour
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
1 teaspoon salt
1 teaspoon cinnamon
1 cup melted butter, or other shortening
1 cup granulated sugar
½ cup sifted brown sugar, firmly packed
2 eggs
2 cups shredded coconut
½ cup sweet milk

1. Sift, then measure the flour. Sift again with the baking soda, salt
and cinnamon.

2. Combine melted shortening, granulated sugar, brown sugar, well

beaten eggs, coconut and milk. Reserve part of coconut for
garnish if desired.

3. To this mixture blend in the dry ingredients.

4. Form into two rolls 6 inches long. Wrap in wax paper. Place in
refrigerator until thoroughly chilled or as needed.

5. Cut ¼ inch slices from roll as required. Bake in hot oven.

Amount: 4 dozen cookies Temperature: 425° F. Time: 5-

8 minutes
See page 20

SOFT MOLASSES COOKIES

4½ cups all-purpose flour
2 teaspoons Arm & Hammer or Cow Brand Baking Soda
3 teaspoons ginger
1 teaspoon salt
1 cup butter, or other shortening
1 cup sifted brown sugar, firmly packed
2 eggs
¾ cup molasses
¾ cup sour milk
Granulated sugar

1. Sift, then measure the flour. Sift again with the baking soda,
ginger and salt.

2. Cream shortening, add sugar gradually and beat until light and
fluffy.

3. Blend in the well beaten eggs. Then add molasses and continue
beating.

4. Alternately add the dry ingredients with the milk, beating until
smooth after each addition.

5. Chill dough in refrigerator several hours.

6. Turn onto floured board. Roll to ¼-inch thickness and cut with
scalloped cooky cutter, or form a roll of the dough and cut slices
¼ inch thick. Sprinkle with granulated sugar.

7. Place on greased baking sheet. Bake in a hot oven.

Amount: 3 dozen, 3-inch cookies Temperature: 400° F. Time:

12 minutes

20
 21

FRUIT COOKIES
3½ cups all-purpose flour
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
1 teaspoon cinnamon
1 teaspoon nutmeg
¾ cup butter
1 cup sugar
2 eggs
¾ cup molasses
1 cup raisins
1 cup nutmeats, coarsely cut

1. Sift, then measure the flour. Sift three times with the baking soda,
salt and spices.

2. Cream the butter until light and lemon colored. Add sugar
gradually.

3. Slowly add the well beaten eggs, then the molasses, blending
thoroughly.

4. Add the dry ingredients, beating until smooth.

5. Last, stir in the raisins and nuts.

6. Chill in refrigerator until firm enough to handle.

7. Turn onto a lightly floured board. Roll as thin as possible without

causing dough to break. Cut with large size, floured cutter.

8. Bake on an ungreased baking sheet in a hot oven.

 Amount: 3½ dozen cookies Temperature: 425° F. Time: 8-
10 minutes

FROSTED CHOCOLATE DROPS

1¾ cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
½ cup butter, or other shortening
¾ cup sugar
1 egg
2 squares (2 ounces) unsweetened chocolate
1 teaspoon vanilla
½ cup sweet milk
½ cup nutmeats, coarsely cut

1. Sift, then measure the flour. Sift three times with the baking soda
and salt.

2. Cream the butter until light and lemon colored. Add sugar
gradually, beating after each addition.

3. Slowly add the well beaten egg, then the chocolate which has
been melted and cooled.

4. Stir vanilla into the milk. Alternately add dry ingredients and
liquid, beating until smooth after each addition. Stir in nutmeats.

5. Drop by spoonfuls on ungreased baking sheet. Bake in hot oven.

6. When cool, frost with Soft Chocolate Frosting.

Amount: 3 dozen cookies Temperature: 425° F. Time: 8-

10 minutes
See page 20
 22

OLD FASHIONED MOLASSES COOKIES

8 cups all-purpose flour
4 teaspoons Arm & Hammer or Cow Brand Baking Soda
¼ teaspoon salt
1 tablespoon ginger
1 teaspoon cinnamon
3 cups molasses
1 cup lard, melted
½ cup butter, melted
10 tablespoons boiling water
Granulated sugar

1. Sift, then measure the flour. Sift three times with the baking soda,
salt and spices.

2. Combine the molasses, melted shortening and boiling water.

3. To these liquid ingredients, add 4 cups of dry ingredients and

blend well.

4. Add remaining 4 cups of dry ingredients gradually, beating well

after each addition.

5. Let stand in a cool place about 1 hour.

6. Turn onto a lightly floured board. Roll ¼ inch thick. Cut with
large, floured cooky cutter. Sprinkle with granulated sugar. Bake in
hot oven.

Amount: 5 dozen cookies Temperature: 425° F. Time:

15 minutes
 CRISP WHITE SUGAR COOKIES
4 cups all-purpose flour
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
1½ cups sugar
1½ cups butter, or other shortening
½ cup sour milk or buttermilk
2 eggs
1 teaspoon vanilla

1. Sift, then measure the flour. Sift again with the baking soda, salt
and sugar.

2. Cut the shortening into the dry ingredients until it is as fine as

corn meal.

3. Combine milk, slightly beaten eggs and vanilla.

4. Add the dry ingredients to the liquid ingredients, beating until

smooth.

5. Cover dough closely with wax paper and chill in refrigerator

overnight or several hours.

6. Then turn dough on a lightly floured board and roll thin. Cut with
a floured cooky cutter. Garnish. Keep dough cold as it becomes
sticky and hard to handle when warm.

7. Bake on ungreased baking sheet in a hot oven.

8. Remove to cooling rack. They will crisp as they cool.

Amount: 4 dozen large cookies Temperature: 425° F. Time: 8-

10 minutes
See page 20
 23

DOUGHNUTS
4 cups all-purpose flour
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
1 teaspoon salt
¼ teaspoon cinnamon
½ teaspoon nutmeg
2 eggs
2 tablespoons shortening, melted
1 cup sugar
1 cup sour milk

1. Sift, then measure the flour. Sift three times with the baking soda,
salt and spices.

2. Beat eggs slightly. Combine beaten eggs, shortening, sugar and

sour milk.

3. Add flour mixture, stirring as little as possible. Chill.

4. Turn onto floured board. Roll or pat ⅓ inch thick. Cut with floured
doughnut cutter.

5. The fat, when ready for frying doughnuts, should be 360°-375° F.,
or it should brown a cube of bread in 60 seconds.

6. Carefully drop each doughnut into the fat to prevent splashing.

Fry not more than 4 or 5 doughnuts at one time or fat will be
cooled too quickly. Fry to a delicate brown, turning doughnuts
once.

7. Drain on unglazed paper and sprinkle with sugar.

Amount: 2½ dozen See page 20

 RAISIN ROCKS
2 cups all-purpose flour
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
1 teaspoon salt
½ teaspoon cloves
1 teaspoon cinnamon
½ teaspoon nutmeg
½ cup butter, or other shortening
½ cup sugar
1 egg
½ cup sour milk
½ cup molasses
1 cup seedless raisins or currants
½ cup nutmeats, coarsely chopped

1. Sift, then measure flour. Sift three times with baking soda, salt
and spices.

2. Cream the butter until light and lemon colored. Add sugar
gradually, beating after each addition.

3. Add the unbeaten egg, blending well.

4. Combine milk and molasses. Alternately add dry ingredients and

the liquid, beating until smooth after each addition.

5. Add raisins and nuts. Drop by spoonfuls on ungreased baking

sheet. Bake in hot oven.

Amount: 3 dozen Rocks Temperature: 400° F. Time: 10-

12 minutes
See page 20

24
 25

Biscuits

SODA BISCUITS
2 cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
4 tablespoons shortening
¾ cup sour milk or buttermilk (about)

1. Sift, then measure flour. Sift again with the baking soda and salt.

2. Using the finger tips or a pastry blender, rub or cut shortening

into the dry ingredients until the mixture resembles coarse corn
meal.

3. To sour ¾ cup sweet milk artificially and quickly, place 1

tablespoon lemon juice or vinegar (preferably white vinegar as it
makes a whiter biscuit) in a measuring cup, fill ¾ full with sweet
milk and mix well.

4. Make a well in the center of the mixture and turn in the sour milk
or buttermilk all at once, reserving about 1 tablespoon of the
liquid as it may not be required.
5. Then stir to make a soft dough as quickly as possible, using a
fork. Add remainder of liquid if necessary.

6. As soon as the flour has been gathered together, turn the dough
onto a floured board. The dough should be stiff but soft to the
touch and not sticky.

7. Knead the dough lightly for about 30 seconds, using the palm of
the hand and finger tips.

8. Then pat or roll to a thickness of about ½ inch. Cut with floured

biscuit cutter.

9. Place biscuits on ungreased baking sheet. Bake in hot oven.

Amount: 12—2 inch biscuits Temperature: 475° F. Time: 12-

15 minutes See page 24

CHEESE TEA BISCUITS

1½ cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
4 tablespoons shortening
1 cup grated cheese
¾ cup sour milk or buttermilk

1. Sift, then measure flour. Sift again with the baking soda and salt.

2. Cut or rub in shortening until it is as fine as coarse corn meal. Add

cheese to this mixture.

3. Add sour milk, stirring quickly to form a soft dough.

4. Drop by teaspoonfuls onto a baking sheet. Bake in hot oven.

 Amount: 18 small biscuits Temperature: 475° F. Time:
12 minutes

26

COFFEE CAKE
2½ cups all-purpose flour
½ teaspoon salt
1 cup sifted brown sugar, firmly packed
½ cup butter, or other shortening
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
1 teaspoon cinnamon
1 egg
¾ cup sour milk or buttermilk

1. Sift, then measure flour. Sift again with salt. Add brown sugar and
mix well.

2. Cut or rub in shortening until it resembles coarse crumbs. Reserve

¾ cup of crumbs for topping.

3. To remainder, add baking soda and cinnamon. Mix well.

4. Combine well beaten egg and sour milk. Then add liquid to dry
ingredients. Stir only until blended.

5. Turn into a greased pan. Sprinkle with the ¾ cup crumbs and
additional cinnamon. Bake in hot oven. Serve hot.

Amount: 8 × 8 inch pan Temperature: 400° F. Time: 30 minutes

CINNAMON BUNS
 2 cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
1 tablespoon sugar
4 tablespoons shortening
¾ cup sour milk or buttermilk (about)
Butter
¼ cup sugar
½ teaspoon cinnamon

1. Sift, then measure flour. Sift again with the baking soda, salt and
sugar.

2. Cut or rub in shortening until it is as fine as coarse corn meal.

3. Add enough sour milk to make a stiff dough.

4. Turn onto a floured board. Knead slightly.

5. Roll into a rectangle ¼ inch thick. Spread with soft butter.

Sprinkle with sugar and cinnamon.

6. Roll as for jelly roll. Cut in slices ¾ inch thick. Spread an

additional tablespoon butter in the bottom of the pan and sprinkle
liberally with sugar. Add a few pecans, if desired.

7. Place rolls, cut side down, on sugar mixture. Bake in hot oven.
Turn out of pan immediately. Serve sugared side up.

8. Brown sugar may be used in place of white sugar to make

butterscotch rolls.

Amount: 12 buns Temperature: 475° F. Time: 15-20 minutes

See page 24

27
 INDIVIDUAL SHORT CAKES
2 cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
⅓ cup shortening
¾ cup sour milk or buttermilk (about)
Butter
Strawberries, crushed and sweetened

1. Sift, then measure flour. Sift again with the baking soda and salt.

2. Cut or rub in shortening until it is as fine as coarse corn meal.

3. Add enough sour milk to make a stiff dough. Turn onto a floured
board. Knead slightly.

4. Roll ¼ inch thick. Cut with 3-inch floured biscuit cutter.

5. Place half of biscuits on ungreased baking sheet. Brush with

melted butter. Place remaining biscuits on top to form a second
layer. Again brush with melted butter. Bake in hot oven.

6. Break open and put fruit between and on top of layers. Garnish
with whipped cream if desired.

Amount: 6 servings Temperature: 475° F. Time: 15 minutes

QUICK ROLLS
2 cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
2 tablespoons shortening
 ¾ cup sour milk or buttermilk (about)
Melted butter

1. Sift, then measure flour. Sift again with the baking soda and salt.

2. Cut or rub in shortening until it is as fine as coarse corn meal.

3. Add enough milk to make a stiff dough. Turn onto a floured

board. Knead for 2 or 3 minutes.

4. Roll ¼ inch thick. Cut with 2-inch cutter, well floured. Fold in half,
pressing edges firmly together.

5. Place slightly apart on a greased pan. Brush with melted butter,

cover and let stand 20 minutes in a warm place.

6. Bake in hot oven 10 minutes, then brush again with melted butter
and complete baking 10 to 15 minutes. Brush with melted butter
once more. Serve immediately.

Amount: 12 rolls Temperature: 475° F. Time: 20-25 minutes

See page 24

28

LEMON CLOVER ROLLS

2 cups all-purpose flour
¾ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
¼ cup sugar
⅓ cup shortening
½ cup sweet milk
3 tablespoons lemon juice

1. Sift, then measure flour. Sift again with the baking soda, salt and
sugar.
2. Cut or rub in shortening until it is as fine as coarse corn meal.

3. Add the combined milk and lemon juice, stirring quickly to form a
soft dough.

4. Turn onto a lightly floured board. Knead slightly.

5. Form dough into balls about the size of marbles. Place 3 balls in
each muffin tin. Sprinkle with sugar. Bake in hot oven.

Amount: 12 rolls Temperature: 450° F. Time: 20 minutes

APPLE DUMPLING
2 cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
⅓ cup shortening
¾ cup sour milk or buttermilk (about)
1½ cups diced apples
Sugar and cinnamon
Butter

1. Sift, then measure flour. Sift again with the baking soda and salt.

2. Cut or rub in shortening until it is as fine as coarse corn meal.

3. Add enough sour milk to make a stiff dough.

4. Turn onto floured board. Knead slightly.

5. Roll into a rectangle about 20 inches long and 10 inches wide. Cut
into eight 5-inch squares.
6. Place a small amount of apple in the center of each square.
Sprinkle lightly with sugar and cinnamon. Dot generously with
butter. Fold corners of square toward the center and join them
over the apples. Place in greased baking pan. Bake in hot oven 15
minutes.

7. Then pour over them a syrup of 1 cup sugar and ½ cup water
that has been heated until all sugar is dissolved. Return to oven
and bake 15 minutes longer. Serve hot with Hard Sauce.

Amount: 8 dumplings Temperature: 425° F. Time: 30 minutes

See page 24

29

CREAM SCONES
2 cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
¾ teaspoon salt
2 tablespoons sugar
4 tablespoons shortening
Grated rind of 1 orange (optional)
¾ cup sweet thin cream or top milk
4 teaspoons vinegar
1 egg

1. Sift, then measure flour. Sift again with the baking soda, salt and
sugar.

2. Cut or rub in shortening until it is as fine as coarse corn meal. Add

orange rind.

3. Combine cream and vinegar. Add to flour mixture, stirring quickly

to form a stiff dough. White vinegar makes a whiter product.
4. Turn onto floured board. Knead slightly. Roll ⅜ inch thick. With a
sharp knife, cut in diamond shapes. These may be cut in half
lengthwise if desired. Brush thickly with slightly beaten egg.

5. Place on ungreased baking sheet. Bake in hot oven.

Amount: 12 scones Temperature: 475° F. Time: 10-12 minutes

HAM ROLLS
2 cups all-purpose flour
½ teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
⅓ cup shortening
¾ cup sour milk or buttermilk (about)
1½ cups boiled ham, ground
¼ teaspoon dry mustard
Butter

1. Sift, then measure the flour. Sift again with the baking soda and
salt.

2. Cut or rub in the shortening until it is as fine as coarse corn meal.

3. Add enough sour milk, stirring quickly, to make a soft dough.

4. Then turn onto a floured board. Knead slightly.

5. Roll into a rectangle 10 inches by 6 inches. Spread with soft

butter, then with the ground ham which has been mixed with the
mustard.

6. Fold the dough into three layers, folding the long sides toward
each other. Flatten slightly with rolling pin by rolling lengthwise.
Cut with a sharp knife into strips 1 inch wide.
7. Stand rolls about ½ inch apart on baking sheet. Bake in hot oven.

Amount: 12 rolls Temperature: 475° F. Time: 15-20 minutes

30
 Muffins

WHOLE WHEAT MUFFINS

2 cups whole wheat flour
1 teaspoon Arm & Hammer or Cow Brand Baking Soda
½ teaspoon salt
4 tablespoons sugar
½ cup raisins
1 egg, well beaten
1½ cups sour milk or buttermilk
3 tablespoons shortening

1. Combine flour, baking soda, salt, sugar and raisins. Mix well.

2. Combine well beaten egg, milk and melted shortening.

3. Add the liquid ingredients to the dry ingredients, stirring only until
dry ingredients are dampened.

4. Fill greased muffin tins ⅔ full. Bake in hot oven.

Amount: 12 muffins Temperature: 425° F. Time: 20-25 minutes

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