Synthesis of Ti 2SC phase using iron disulfide or iron sulfide post-treated with acid

Article abstract of DOI:10.1111/jace.13457

This study reports a viable method for the synthesis of Ti₂SC phase using iron disulfide or iron sulfide as sulfur source and a post-treatment with acid. The reaction routes to Ti₂SC phases starting from two different chemical compositions of 2Ti- FeS₂ -2TiC and Ti-FeS -TiC were in detail explored and compared through the analysis of X-ray diffraction, thermo-gravimetry/ differential scanning calorimetry, and scanning electron microscopy results. Unlike the Ti-FeS-TiC composition, the reaction route from 2Ti-FeS₂-2TiC composition contained an extra decomposition step in which FeS₂ transformed to activated FeS and released molecular state sulfur at temperature around 500° C. The latter at this temperature could successfully trigger the reaction of Ti-S-TiC to form Ti₂SC phase, which was an analogous self-propagating high-temperature synthesis with a high transient temperature. On the contrary, only trace of Ti₂SC phase could be obtained at temperature as high as 1200° C from the Ti-FeS-TiC composition. The main impurity phases from these iron disulfide reactant systems were Fe and FeS, and they could be easily purified by dissolution in H₂SO₄solution, which resulted in Ti₂SC phase with a minor TiC phase in the final product.

Full text of DOI:10.1111/jace.13457

J. Am. Ceram. Soc., 1–6 (2015)
DOI: 10.1111/jace.13457
© 2015 The American Ceramic Society
ournal
J
Synthesis of Ti2SC Phase Using Iron Disulfide or Iron Sulfide Post-treated with
Acid
Ke Chen,‡ Qun Ye,‡ Jie Zhou,‡ Lu Shen,‡ Jianming Xue,§ and Qing Huang‡,†
‡Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Chinese
Academy of Sciences, Ningbo, Zhejiang 315201, China
§State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
This study reports a viable method for the synthesis of Ti2SC
phase using iron disulfide or iron sulfide as sulfur source and a
post-treatment with acid. The reaction routes to Ti2SC phases
starting from two different chemical compositions of 2Ti–
FeS2–2TiC and Ti–FeS–TiC were in detail explored and
compared through the analysis of X-ray diffraction, thermo-
gravimetry/differential scanning calorimetry, and scanning elec-
tron microscopy results. Unlike the Ti–FeS–TiC composition,
the reaction route from 2Ti–FeS2–2TiC composition contained
an extra decomposition step in which FeS2 transformed to acti-
vated FeS and released molecular state sulfur at temperature
around 500°C. The latter at this temperature could successfully
trigger the reaction of Ti–S–TiC to form Ti2SC phase, which
was an analogous self-propagating high-temperature synthesis
with a high transient temperature. On the contrary, only trace
of Ti2SC phase could be obtained at temperature as high as
1200°C from the Ti–FeS–TiC composition. The main impurity
phases from these iron disulfide reactant systems were Fe and
FeS, and they could be easily purified by dissolution in H2SO4
solution, which resulted in Ti2SC phase with a minor TiC
phase in the final product.
(a = b = 0.3210 nm and c = 1.120 nm)1 and a stronger bond
strength in the M–A bond (i.e. Ti–S bond).11–14 These fea-
tures result in high values of Young’s moduli (316 GPa15),
shear moduli (125 GPa16), and hardness (8 Gpa15).12,17,18 In
addition, Ti2SC bulk also exhibits the highest thermal con-
ductivity [60 Wꢀ(mꢀK)ꢁ1 19] and the resistivity (0.52 lΩ m16)
at room temperature to most MAX phases (n = 1–3).5,16
Kulkarni and Merlini’s work showed that Ti2SC was ther-
mally stable at 950°C in Ar atmospheres20 and even after pro-
cessed at 1600°C for 20 h in Ar atmosphere it was still
stable15. That means the Ti2SC can be used as promising
protective coating on steel or other material to prevent the
sulfur corrosion, since Ti2SC phase is a stable product of reac-
tants containing sulfur material. Moreover, transition-metal
dichalcogenides added with C, N, and/or some metal coating
(most commonly W–S–C and Mo–S–C) have well-known
excellent self-lubrication properties.21–23 Sundberg’s work
showed that the Ti–S–C nanocomposite coating could also
lower the friction levels and prolong the lifetime even against
the tungsten-coated steel ball, which could be explained by
the tribo-chemically activity of Ti–S–C nanocomposite coat-
ing.24 Hence, the Ti–S–C coating (includes Ti2SC phase) may
find some applications in the tribology field.
I. Introduction
In fact, Ti2SC was first observed as a hard inclusion in Ti
alloyed steel25,26 and then also found as micro-Y-phase in
nickel-based superalloys27,28. However, to date, there are
few studies discussing the synthesis of pure Ti2SC phase.
P. Wally et al.26,29 utilized the Cl6C6 as catalyst to synthesize
Ti2SC powders directly by combustion synthesis of elemental
mixture of Ti–S–C. The ignition temperature was between
700°C and 800°C, and the maximum temperature of the reac-
tion route was above 1800°C. However, owing to the volatili-
zation of sulfur, the purity of Ti2SC was poor. Li et al.
reported TiC and Ti3S4 as main impurities after combustion
synthesis even after the addition of excess sulfur in raw mate-
rials.30 Zhu and Mei et al.31,32 used TiS2 to provide the
sulfur source and they synthesized pure Ti2SC powders
from Ti–TiS2–C mixture at temperature as high as 1600°C.
Nevertheless, the raw material TiS2 is hard to handle and
very expensive that is not in favor of further research and
industry application.
AX phase is a terminology for a family of ternary
ceramics, in which M is an early transition metal, A is
M
an A-group element and X is carbon or/and nitrogen.1–5
Their crystal structures belong to P63/mmc (no. 194) space
group, and consist of alternative near-close-packed layers of
M6X octahedral that interleafed with a layer of pure A
atoms.1,5 Due to the specific layered crystal structure, the
MAX phases possess unique properties combining those of
the metals and the ceramics:1,2,5,6 a good electrical and ther-
mal conductivity, good machinability, low hardness, thermal
shock resistance, and damage tolerance inherited from the
metals, and
a high elastic modulus, high-temperature
strength, an oxidation, and corrosion resistance relevant to
ceramics. Recent researches have also shown that the MAX
phases have a good performance to tolerate irradiation dam-
age and molten salt corrosion.7–9 Therefore, the MAX phases
have the potential to become a new kind of structural mate-
rial candidates for the future nuclear reactor system.
In this study, we introduce an available method to synthe-
size Ti2SC using iron disulfide or iron sulfide as sulfur
source. Two reaction systems, 2Ti–FeS2–2TiC and Ti–FeS–
TiC, have been in parallel studied to reveal the formation
mechanism of Ti2SC phase at low temperature in the former
composition.
Ti2SC was discovered by Kudielka and Rohde in 1960s.10
Distinguishing to the other MAX phases, Ti2SC has two dis-
tinctive structural characteristics: a much smaller c/a value
R. Koc—contributing editor
II. Experimental Procedures
The Ti2SC phase was synthesized using commercially available
powders. Titanium (99.5% purity, 300 mesh, Targets Research
Center of General Research Institute for Nonferrous Metals,
Beijing, China), Titanium carbide (99.5% purity, 2.6 lm,
Manuscript No. 35522. Received August 25, 2014; revised December 10, 2014;
approved December 12, 2014.
†Author to whom correspondence should be addressed. e-mail: huangqing@nimte.
ac.cn
1

2
Journal of the American Ceramic Society—Chen et al
Beijing Xingrongyuan Co. Ltd, Beijing, China), and iron disul-
fide (95% purity, the main impurity is 3% Si, 20–25 lm, Strem
Chemicals, Newburyport, MA) or iron sulfide (99% purity,
200 mesh, J&K Scientific Ltd, Beijing, China), were mixed with
the molar ratio of 2:2:1 or 1:1:1 by planetary ball mill, respec-
tively. The charge ratio of powders to agate balls was 1:3. And
they were blended in a Polytetrafluoroethylene jar with abso-
lute ethanol at 200 rpm for 12 h. The ground powder mixture
was then cold-pressed in a graphite mold. The green pellets
were further calcined in a Pulse-Electric-Current-Aided sinter-
ing device (HP D 25/3; FCT Group, Rauenstein, Germany) in
Ar atmosphere. No pressure was applied on the green body
throughout the synthesis. The temperatures were held at 500°C
for 1 min, and then held for 5 min (which is an empirical
value, according to our previous work.33) at target tempera-
tures of 500°C, 600°C, 800°C, 1000°C, 1200°C, 1400°C, and
1500°C, respectively [more details could be found in Fig. 3(a)].
Then, the as-synthesized products were pulverized and
immersed in H2SO4 solution (1 mol/L) to get rid of the iron
particles and iron sulfide particles.
of reaction was traced by thermal analysis (TG/DSC; NET-
ZSCH STA449F3 Jupiter, Selb, Germany) from room tem-
perature to 1500°C with a heating rate of 10°C /min in Ar
atmosphere.
III. Results and Discussion
The X-ray diffractograms of the powders synthesized from
2Ti–FeS2–2TiC and Ti–FeS–TiC compositions at different
temperatures are shown in Fig. 1. At 400°C, there was no
obvious phase change compared with original mixture in
both reactant systems. However, there was a dramatic differ-
ence in phase evolution when temperature was higher than
500°C. Figure 1(a) shows the appearance of Ti2SC in the
2Ti–FeS2–2TiC system even at 500°C that should be the
lowest temperature to form Ti2SC phase ever reported. More
specifically, in the initial stage (500°C–600°C), sulfur
atom should be gradually released from FeS2 molecule since
FeS2 phase was not thermally stable in this temperature
range34,35 [Eq. (1)]. The thermodynamically stable FeS35 was
expected to be observed in the product as the decomposition
residue [Fig. 1(a)]. Indeed, it has been reported that pyrite
(FeS2) commonly used in thermally activated battery could
experience a transformation to porous FeS after thermal
decomposition.36,37 The released molecular sulfur in uniform
mixed 2Ti–FeS2–2TiC composition could immediately and
fully react with Ti and TiC to form Ti2SC phase [Eq. (2)],
which was a fierce exothermic reaction according to P.
The synthetic powders were characterized by X-ray diffrac-
tometer (XRD; Bruker AXS D8 Advance, Karlsruhe, Ger-
many) with Cu Ka radiation and their spectra were collected
at a step scans of 0.02° 2h and a step time of 0.2 s. The
microstructure was observed by field emission scanning elec-
tron microscope (SEM; FEI QUANTA 250 FEG, Hillsboro,
OR) equipped with energy dispersive spectroscopy (EDS,
Oxford Instruments, Oxford, UK). In addition, the evolution
(a)
(b)
Fig. 1. X-ray diffraction spectra of products originated from (a) 2Ti–FeS2–2TiC and (b) Ti–FeS–TiC at different temperatures.

Synthesis of Ti2SC Phase
3
(a)
(b)
Fig. 2. Phase content variation during the process plotted as a function of sintering temperature: (a) is the 2Ti–FeS2–2TiC reactant system, (b)
is the Ti–FeS–TiC reactant system.
Wally’s work26,29. That was to say, the first reaction path
[shown in Fig. 2(a)] to form Ti2SC phase in 2Ti–FeS2–2TiC
composition was an analogous self-propagating high-temper-
ature synthesis, whose trigger temperature was around
500°C. On the other hand, these iron sulfide particles should
have a high reactivity and an increase in surface area after
the release of sulfur from the large FeS2 particles as the
analysis above, which could promote the following solid-state
reactions. With the local high temperature caused by the
fierce exothermic reaction of Ti–S–TiC [Eq. (2)], parts of the
porous FeS phase reacted with Ti and TiC soon after forma-
tion, and resulted in the formation of Ti2SC and Fe [Eqs. (3)
and (4)]. Therefore, the FeS phase formed by the release of
sulfur from FeS2 phase at 500°C seems to play a key role on
the reactivity of intermediate phase FeS. The intentional
dwelling for 1 min at 500°C obviously decreased the amount
of TiC phase in the final product, meaning FeS could be
fully converted from FeS2 phase and totally exhausted to
form Ti2SC phase. Meanwhile, extra FeS continued to react
with Ti metal at high temperature to form TiS and iron
[Eq. (3)]. The latter fact was clearly reflected by the increase
in the diffraction intensity of these resultants in the product
above 600°C. Beyond 1200°C, the Ti2SC phase became pre-
dominant owing to the reaction between TiS and TiC
[Eq. (4)]31,32. Hence, we can describe the synthesis reaction
into four main steps as follows:
tion again. The formation of TiS via FeS and Ti also agreed
with the assumption of Eq. (3) in the 2Ti–FeS2–2TiC reac-
tant system. The solid-state reaction between TiS and TiC
was controlled by the atomic diffusion and the saturated
vapor pressures. At temperature higher than 1200°C, the sat-
urated vapor pressures of TiS (Tmelting = 1780°C) was higher
than that of TiC (Tmelting = 4820°C), and the formation of
Ti2SC phase became thermodynamically favorable. Based on
the above observations, the reaction route of Ti–FeS–TiC
reactant system can be described as follows:
FeS þ Ti ¼ TiS þ Fe ð800ꢂC ꢁ 1200ꢂCÞ
TiS þ TiC ¼ Ti2SC ð1200ꢂC ꢁ 1500ꢂCÞ
(5)
(6)
To reveal the phase evolution and underlying formation
mechanism of Ti2SC phase, a quantitative analysis of XRD
spectra by Rietveld Refinement technique was performed on
these two reactant systems (shown in Fig. 2). In the 2Ti–
FeS2–2TiC reactant system [Fig. 2(a)], the FeS2 raw material
was completely consumed at temperature of 500°C [Eq. (1)].
The formation of Ti2SC phase at 500°C was accompanied by
the consumption of Ti raw material as well as TiC. The
amount of formed Ti2SC was seemly inversely proportional
to the quantities of these two phases [Eq. (2)]. In addition,
the weight percentage of iron kept almost constant at tem-
perature over 800°C, where FeS phase totally disappeared.
The latter observation meant that displacement reaction
(Eq. 3) could be accomplished in the temperature range of
500°C–800°C. At the temperature higher than 1200°C, Ti2SC
phase suddenly increased at the sacrifice of TiC and TiS
phases [Eq. (4)]. However, in the case of Ti–FeS–TiC reac-
tant system [Fig. 2(b)], Ti2SC phase could also be detected in
the high-temperature range, with the same trend of the
decrease in TiC and TiS phases similar to 2Ti–FeS2–2TiC
reactant system. It was interesting to note that about 75% of
Ti2SC phase resulting from the 2Ti–FeS2–2TiC reactant sys-
tem was formed through reaction path 1 [Eq. (2)] which was
below 1200°C, and all Ti2SC phase resulting from the Ti–
FeS–TiC reactant system originated from reaction path 2
[Eq. (6)] which was over 1200°C. A hint could be drawn
from the variation in the amount of TiC phase in 2Ti–FeS2–
2TiC reactant systems since it participated into both reaction
paths: 57% of original TiC was consumed in the path 1 com-
pared with 21% of original TiC in path 2. This was well con-
sistent with the proportion of Ti2SC phase obtained in path
1 and path 2. The phase compositions of final products in
FeS2 ¼ FeS þ 1=2S2 ð500ꢂC ꢁ 600ꢂCÞ
(1)
S þ Ti þ TiC ¼ Ti2SC ð500ꢂC ꢁ 600ꢂCÞ
FeS þ Ti ¼ TiS þ Fe ð500ꢂC ꢁ 1200ꢂCÞ
TiS þ TiC ¼ Ti2SC ð1200ꢂC ꢁ 1500ꢂCÞ
(2)
(3)
(4)
Figure 1(b) represented the phase evolution from the Ti–
FeS–TiC reactant system at different synthesis temperatures.
The mixture reaction was observed at 800°C to form Fe and
TiS phase with the decrease of FeS and TiC phases [Eq. (5)].
The Ti2SC phase appeared at temperature of 1200°C
[Eq. (6)], that is, 700°C higher than that observed in the 2Ti–
FeS2–2TiC reactant system. It was also worth noting that
TiS phase was formed at 800°C in this system, which was
300°C higher than that observed in the 2Ti–FeS2–2TiC reac-
tant system [Eq. (3)]. This highlighted the largely enhanced
reactivity of the porous FeS derived from FeS2 decomposi-

4
Journal of the American Ceramic Society—Chen et al
both two systems are summarized in Table I through the
Rietveld analysis of XRD from Fig. 1.
the decomposition of FeS. This fact could account for a vio-
lent exothermic peak due to the TiS formation in Fig. 3(a).
Two characteristic peaks around 868°C and 1475°C in both
reactant systems [the no. 2 and 4 lines in Fig. 3(b)] were
attributed to the displacement reaction (Eqs. 3 and 5) and
solid-state combination reaction (Eqs. 4 and 6), respectively.
The only difference was that the corresponding reaction tem-
perature of Eq. (5) was much higher than equation Eq. (3).
That was because the FeS in 2Ti–FeS2–2TiC reactant system
produced from decomposition of FeS2 was porous and non-
stoichiometric, but the as-received FeS was well-crystallized
product, which meant the former possessed higher reactivity.
Although Ti2SC phase could be obtained from 2Ti–FeS2–
2TiC reactant system, there were still some impurities left in
The previously mentioned reaction path 1 [Eqs. (1) and
(2)] could also be further corroborated by the sintering curve
and thermogravity/differential scanning calorimetry (TG/
DSC) results (Fig. 3). During the dwelling at 500°C in sinter-
ing curve [Fig. 3(a)], a sharp temperature increase to 800°C
came hard on the heel of the first sharp drop (the actual tem-
perature must be higher than the recorded one since this pro-
cess was transient). The latter was probably due to the
endothermic decomposition reaction of FeS2 [Eq. (1)] and
the former could attribute to the exothermic synthesis reac-
tion of TiS through Ti raw material and the release of sulfur
in Eq. (1), respectively. The intense heat released during TiS
formation might have warranted the further endothermic
reaction between TiS and TiC to generate Ti2SC phase that
normally occurs at high temperature [Eqs. (2) and (4)]. The
temperature instability around 450°C was due to the auto-
feedback of furnace in all reactant system, and had nothing
to do with the synthesis process of Ti2SC phase. However,
there was no endothermic or exothermic behavior in the sin-
tering curve of Ti–FeS–TiC reactant system. The decomposi-
tion of FeS2 at 500°C was also of evidence in the TG/DSC
results [Fig. 3(b)], wherein an endothermic peak at 600°C
(the difference in the temperature was due to the detection
method; pyrometer was employed in the sintering furnace
while thermal couple was used in TG/DSC measurement)
was well recorded in the DSC curve accompanied by a
weight loss in the TG curve [the no. 1 and 2 lines in
Fig. 3(b)]. The mixture powders for TG/DSC measurement
were so loose that S could easily escape, explaining the
weight lose behavior. In the synthesis process, however, the
mixture was pressed into compact green body, and thus S
gas must have reacted with surrounding Ti metal soon after
(b)
(a)
Table I. The Final Compositions of 2Ti–FeS2–2TiC and
Ti–FeS–TiC Systems Before and After Acid Treatment by
Rietveld Analysis of XRD (1500°C for 5 min)
Weight content (wt%)
Reliability factors
Samples
Ti2SC
TiC
Fe
Rwp (%)
2Ti-FeS2-2TiC
2Ti-FeS2-2TiC
post-treated with acid
Ti-FeS-TiC
Ti-FeS-TiC
post-treated with acid
78.46 6.96 14.58
89.19 10.81
6.29
10.11
—
Fig. 4. X-ray diffraction and microstructure of 2Ti–FeS2–2TiC
blended powders synthesized at 1500°C for 5 min: (a) synthetic
powders at 1500°C, (b) synthetic powders at 1500°C, after H2SO4
solution (1 mol/L) treatment. The inset in center of (a) is the
elemental mapping of Fe in specific region of microstructure.
63.42 6.34 30.24
91.01 9.99
4.55
7.54
—
(a)
(b)
Fig. 3. (a) Sintering curve of 2Ti–FeS2–2TiC reactant system, (b) TG-DSC curves of 2Ti–FeS2–2TiC reactant system and Ti–FeS–TiC reactant
system from room temperature to 1500°C with the heating rate of 10°C/min in Ar atmosphere.

Synthesis of Ti2SC Phase
5
impurities left were the same as 2Ti–FeS2–2TiC reactant sys-
tem. Table I exhibits the final compositions of these two
systems after acid treatment and Fig. 5 displays one of the
results of the Rietveld analysis.
Table II. The EDS Results of the Particles in Fig. 4
Atomic %
Ti
S
C
Fe
Si†
Totals
k1
k2
k3
63.22
10.07
63.38
35.26
5.86
35.93
0.76
0.28
0.70
0.75
81.23
0
0
2.56
0
99.99
100.00
100.01
IV. Conclusions
†The little content of Si came from the raw material FeS2, which contained
3% Si impurity.
FeS2 and FeS were used to synthesize Ti2SC phase. The FeS2
decomposed around 500°C and the released sulfur favored
the exothermic reaction of S and Ti to form TiS phase. The
heat released during TiS formation also promoted the solid-
state combination between TiS and TiC to obtain Ti2SC
phase, which was normally accomplished in the traditional
synthesis at temperature higher than 1200°C as observed in
the Ti–FeS–TiC system. The main impurities left in the prod-
ucts were Fe and FeS phases besides TiC, and could be effec-
tively removed by dissolution treatment in H2SO4 solution
(1 mol/L). This synthesis approach of Ti2SC phase will
largely promote the potential application such as corrosion
protection coating.
Acknowledgments
This research is supported by the National Natural Science Foundation of
China (91226202). We are grateful to Yi Feng and Kesong Xiao of HeFei
University of Technology for carrying out the TG-DSC measurements. We
also would like to thank Yongchun Ma for SEM and X-ray scan area map-
ping measurements and Jie Sun for Rietveld analysis of XRD.
References
1M. W. Barsoum, “The M(N+1)AX(N) Phases: A New Class of Solids; Ther-
modynamically Stable Nanolaminates,” Prog. Solid State Chem., 28, 201–81
(2000).
Fig. 5. The image of the Rietveld analysis for 2Ti–FeS2–2TiC as-
synthesized powders (1500°C for 5 min) after H2SO4 solution
(1 mol/L) treatment.
2M. W. Barsoum and T. El-Raghy, “The MAX Phases: Unique New Car-
bide and Nitride Materials - Ternary Ceramics Turn Out to be Surprisingly
Soft and Machinable, Yet Also Heat-Tolerant, Strong and Lightweight,” Am.
Sci., 89, 334–43 (2001).
3J. Y. Wang and Y. C. Zhou, “Recent Progress in Theoretical Prediction,
Preparation, and Characterization of Layered Ternary Transition-Metal Car-
bides,” Annu. Rev. Mater. Res., 39, 415–43 (2009).
the products. To improve the purity, the as-synthesized pow-
ders were treated with H2SO4 solution (1 mol/L). Figure 4
exhibits the XRD spectra and microstructure of products
that were synthesized at 1500°C for 5 min before and after
acid treatment. The ratio of Ti to S in the major dark
regions labeled as k1 and k3 was about 1.8, (closer to 2) (See
Fig. 4 and Table II). As there was no Ti2S phase formed in
the synthesis according to the analysis above, these regions
were identified as Ti2SC phase. The reasons of the C content
lower than 1 at.% were as follows: First, C content obtained
from EDS was not precise due to the detection limit of EDS.
Second, the EDS device utilized had been calibrated by stain-
less steel, and its C content was below 1 at.%. The iron
impurity could be completely dissolved by acid treatment as
shown by the disappearance of diffraction peak in Fig. 4(b).
The SEM imaged obtained using backscattered electron
(BSE) was conclusive for this result (the inset in Fig. 4). The
bright powders (k2) in the as-synthesized product that were
confirmed to be the Fe-rich phase by EDS (Table II). X-ray
scan area mapping analysis of Fe also exhibited the distribu-
tion of Fe, which was labeled as red point [the inset in
Fig. 4(a)]. Those residues were not observed by SEM in the
powders after the acid post-treatment [the inset in Fig. 4(b)].
The other possible impurities, such as FeS2, Ti, and TiC,
might exist in the low-temperature synthesized powders.
However, the amounts of these impurities could be expected
to be controlled by tuning the initial composition of FeS2–
Ti–TiC reactant system. Therefore, it provided a viable
approach to obtain superfine and high-reactivity Ti2SC phase
at temperature range of 500°C–1000°C via composition con-
taining FeS2. Although the TiC phase was resistant to the
acid corrosion, it could be used as strengthening phase in the
further composite sintering. In addition, the Ti2SC phase
synthesized from Ti–FeS–TiC reactant system [Fig. 1(b)]
could also be purified through the acid treatment as the
4P. Eklund, M. Beckers, U. Jansson, H. Hogberg, and L. Hultman, “The M
(n+1)AX(n) Phases: Materials Science and Thin-Film Processing,” Thin Solid
Films, 518, 1851–78 (2010).
5Z. M. Sun, “Progress in Research and Development on MAX Phases a
Family of Layered Ternary Compounds,” Int. Mater. Rev., 56, 143–66 (2011).
6M. W. Barsoum and M. Radovic, “Elastic and Mechanical Properties of
the MAX Phases,” Annu. Rev. Mater. Res., 41, 195–227 (2011).
7L. A. Barnes, N. L. D. Rago, and L. Leibowitz, “Corrosion of Ternary
Carbides by Molten Lead,” J. Nucl. Mater., 373, 424–8 (2008).
8E. N. Hoffman, D. W. Vinson, R. L. Sindelar, D. J. Tallman, G. Kohse,
and M. W. Barsoum, “MAX Phase Carbides and Nitrides: Properties for
Future Nuclear Power Plant in-Core Applications and Neutron Transmutation
Analysis,” Nucl. Eng. Des., 244, 17–24 (2012).
9K. R. Whittle, M. G. Blackford, R. D. Aughterson, S. Moricca, G. R.
Lumpkin, D. P. Riley, and N. J. Zaluzec, “Radiation Tolerance of M(n+1)AX
(n) Phases, Ti3AlC2 and Ti3SiC2,” Acta Mater., 58, 4362–8 (2010).
10H. Kudielka and H. Rohde, “Strukturuntersuchungen an Carbosulfiden
von Titan und Zirkon,” Z. Kristallogr., 114, 447–56 (1960).
11S. X. Cui, W. X. Feng, H. Q. Hu, Z. B. Feng, and H. Liu, “Hexagonal
Ti2SC with High Hardness and Brittleness: A First-Principles Study,” Scripta
Mater., 61, 576–9 (2009).
12Y. L. Du, Z. M. Sun, and H. Hashimoto, “First-Principles Study on Phase
Stability and Compression Behavior of Ti2SC and Ti2AlC,” Phys. B-Condensed
Matter, 405, 720–3 (2010).
13Y. L. Du, Z. M. Sun, H. Hashimoto, and W. B. Tian, “First-Principles
Study on Electronic Structure and Elastic Properties of Ti2SC,” Phys. Lett. A,
372, 5220–3 (2008).
14G. Hug, “Electronic Structures of and Composition Gaps Among the Ter-
nary Carbides Ti2MC,” Phys. Rev. B, 74, 184113 (2006).
15S. Amini, M. W. Barsoum, and T. El-Raghyy, “Synthesis and Mechanical
Properties of Fully Dense Ti2SC,” J. Am. Ceram. Soc., 90, 3953–8 (2007).
16T. H. Scabarozi, S. Amini, P. Finkel, O. D. Leaffer, J. E. Spanier, M. W.
Barsoum, M. Drulis, H. Drulis, W. M. Tambussi, J. D. Hettinger, and S. E.
Lofland, “Electrical, Thermal, and Elastic Properties of the MAX-Phase Ti(2)
SC,” J. Appl. Phys., 104, 033502 (2008).
17T. Liao, J. Y. Wang, and Y. C. Zhou, “Chemical Bonding and Mechani-
cal Properties of M(2)AC (M = Ti, V, Cr, A = Al, Si, P, S) Ceramics from
First-Principles Investigations,” J. Mater. Res., 24, 556–64 (2009).
18A. Bouhemadou and R. Khenata, “Structural, Electronic and Elastic
Properties of M(2)SC (M = Ti, Zr, Hf) Compounds,” Phys. Lett. A, 372,
6448–52 (2008).

6
Journal of the American Ceramic Society—Chen et al
19T. H. Scabarozi, S. Amini, O. Leaffer, A. Ganguly, S. Gupta, W. Tambussi,
28X. B. Hu, Y. B. Xue, S. J. Zheng, Y. L. Zhu, D. Chen, and X. L. Ma,
“Microstructural Characteristics of the Microphase Y-Ti2SC in Nickel-Based
Superalloys,” J. Alloy. Compd., 611, 104–10 (2014).
S. Clipper, J. E. Spanier, M. W. Barsoum, J. D. Hettinger, and S. E. Lofland,
“Thermal Expansion of Select M > n+1 > AX > n (M=Early Transition Metal,
A=A Group Element, X=C or N) Phases Measured by High Temperature x-ray
Diffraction and Dilatometry,” J. Appl. Phys., 105, 013543 (2009).
29P. Wally and M. Ueki, “Combustion Synthesis of Transition Metal Carbo-
sulfides,” J. Solid State Chem., 138, 250–9 (1998).
20S. R. Kulkarni, M. Merlini, N. Phatak, S. K. Saxena, G. Artioli, S.
Amini, and M. W. Barsoum, “Thermal Expansion and Stability of Ti2SC in
Air and Inert Atmospheres,” J. Alloy. Compd., 469, 395–400 (2009).
21W. E. Jamison and S. L. Cosgrove, “Friction Characteristics of Transi-
tion-Metal Disulfides and Diselenides,” Asle Trans., 14, 62–72 (1971).
22A. Nossa and A. Cavaleiro, “The Influence of the Addition of C and N
on the Wear Behaviour of W-S-C/N Coatings,” Surf. Coat. Technol., 142,
984–91 (2001).
30X. Li, B. Y. Liang, and Z. X. Li, “Combustion Synthesis of Ti2SC,” Int.
J. Mater. Res., 104, 1038–40 (2013).
31W. B. Zhu, J. H. Song, and B. C. Mei, “Kinetics and Microstructure Evo-
lution of Ti2SC During in Situ Synthesis Process,” J. Alloy. Compd., 566, 191–
5 (2013).
32W. B. Zhu, B. C. Mei, Y. W. Tu, and J. H. Song, “High Pressure Effect
on Reaction Synthesis of Ti2SC Powder,” Mater. Sci. Nanotechnol. I, 531-532,
312–6 (2013).
23T. Polcar, F. Gustavsson, T. Thersleff, S. Jacobson, and A. Cavaleiro,
“Complex Frictional Analysis of Self-Lubricant W-S-C/Cr Coating,” Faraday
Discuss., 156, 383–401 (2012).
33J. Zhou, F. G. Qiu, L. Shen, F. Z. Li, J. M. Xue, M. W. Barsoum, and Q.
Huang, “Pulse Electric Current- Aided Reactive Sintering of High- Purity
Zr3Al3C5,” J. Am. Ceram. Soc., 97, 1296–302 (2014).
24
J. Sundberg, H. Nyberg, E. Sarhammar, K. Kadas, L. Wang, O. Eriksson,
T. Nyberg, S. Jacobson, and U. Jansson, “Tribochemically Active Ti–C–S
Nanocomposite Coatings,” Mater. Res. Lett., 1, 148–55 (2013).
25K. E. Himmelbauer, “Darstellung und Eigenschaften der Carbosulfide
der Ubergangsmetalle”; Doctoral Thesis, Vienna University of Technology,
1977.
34I. C. Hoare, H. J. Hurst, W. I. Stuart, and T. J. White, “Thermal-Decompo-
sition of Pyrite - Kinetic-Analysis of Thermogravimetric Data by Predictor Cor-
rector Numerical-Methods,” J. Chem. Soc.-Faraday Trans. I, 84, 3071–7 (1988).
35D. Ferro, V. Piacente, and P. Scardala, “Decomposition Enthalpies of
Iron Sulfides,” J. Chem. Thermodynamics, 21, 483–94 (1989).
36P. J. Masset, “Thermal Stability of FeS2 Cathode Material in “Thermal”
Batteries: Effect of Dissolved Oxides in Molten Salt Electrolytes,” Zeitschrift
Fur Naturforschung Section a-a Journal of Physical Sciences, 63, 596–602
(2008).
€
ꢀ
26P. Wally and M. Ueki, “Thermal Stability of Transition Metal Carbo-
sulfides Prepared by Combustion Synthesis,” J. Alloy. Compd., 268, 83–8
(1998).
27C. Sun, R. F. Huang, J. T. Guo, and Z. Q. Hu, “Sulfur Distribution in
K24 Cast Nickel-Base Superalloy and Its Influence on Mechanical-Properties,”
High Temp. Technol., 6, 145–8 (1988).
37P. J. Masset and R. A. Guidotti, “Thermal Activated (“Thermal”) Battery
Technology - Part IIIa: FeS(2) Cathode Material,” J. Power Sources, 177,
595–609 (2008).
h