Applied Clay Science 59–60 (2012) 36–41
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Applied Clay Science
journal homepage: www.elsevier.com/locate/clay
Research paper
Synthesis and characterization of Co–Al–CO3 layered double-metal hydroxides and
assessment of their friction performances
Zhi Min Bai ⁎, Zhen Yu Wang, Tian Guang Zhang, Fan Fu, Na Yang
China University of Geosciences, Beijing, 100083, China
a r t i c l e
i n f o
Article history:
Received 19 July 2011
Received in revised form 3 February 2012
Accepted 6 February 2012
Available online 28 March 2012
Keywords:
Layered double-metal hydroxides
Hydrotalcites
Friction performances
Lubrication and anti-frictional materials
a b s t r a c t
In this paper, Co–Al–CO3 layered double-metal hydroxides (CAC-LDHs) were prepared by co-precipitation
method and characterized by XRD, FT-IR, TG-DSC, SEM. In addition, their frictional features were evaluated
by four-ball friction tester, gear tester and air compressor. The results showed that optimized synthetic conditions of CAC-LDHs were water–ethanol solution media with Co/Al mol ratio of 3:1, crystallization temperature of 120 °C and crystallization time of 5 h. The LDHs have perfect crystals with hexagonal lamella
structures. Most crystallites have disk diameter of 150 – 200 nm and thickness of 20 nm. The d-spcing and
gallery height of CAC-LDHs were 0.77nm and 0.29nm, respectively. Total specific surface area of the sample
is 97 m 2/g and pore volume is 0.14 cm 3/g. As a lubricant, CAC-LDHs can significantly reduce friction coefficient (49.1%) and wear of friction pairs. They can also reduce temperature of lubrication oil (7.4–7.7%) and
energy consumption of driving motor (4.8–7.0%). Accordingly, CAC-LDHs may broadly be used as lubrication
and anti-frictional materials.
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
In recent years, many studies have been conducted with regard
to basic principles and applications of layered silicate minerals,
represented by serpentine, as anti-frictional and self-repairing materials. Experimental results indicate that serpentine may significantly reduce friction coefficient and wear of friction pairs(Shi et
al., 2007; Xu et al., 2009; Yang et al., 2005).A high-strength wearprotection coating may form on the surface of friction pairs during
friction by reacting serpentine with wear debris, components of lubricating media and carbon materials. The coating has combined
features of structure strengthening, inter-metallic enforcement and
replace hardening; Serpentine may also serve as a catalyst to
clean the friction surface and to maintain wear surfaces “in activation”(Yang and Bai, 2010; Zhang et al., 2009). However, ultra-fine
comminution, surface modification, activating treatment and some
other complicated processing may be required before natural minerals be used as anti-frictional and self-repairing materials. In addition, these technologies are characterized by difficulties in
controlling over granularity of the powder, adjustment of mineral
compositions and implementation of intercalation technologies (Li
et al., 2008). Because synthetic minerals in nano-meter scale have
superior features than natural minerals as anti-frictional and self-
⁎ Corresponding author. Tel.: + 86 10 82323201; fax: + 86 10 82322974.
E-mail address: [email protected] (Z.M. Bai).
0169-1317/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.clay.2012.02.003
repairing materials, they have attracted more attentions in recent
years (Li, 2007).
Layered double-metal hydroxides (LDHs) are known as hydrotalcite compounds (HTlcs) or hydrotalcites. They are layered compounds composed by metal hydroxide sheet with positive charge
and interlayer space filled with anion with negative electric
charge (Miyata, 1983). LDHs are represented by the general formula [M II1 − xM IIIx (OH)2] x + [A nx/n · mH2O] x−, where M II is a divalent cation (Mg 2+ and/or Ni 2+,Zn 2+,Co 2+,Cu 2+); M III is a
trivalent cation (Al 3+and/or Fe 3+, Cr 3+), and A is an anion with
charge n (OH −,CO32−,NO 3−,Cl\,SO42−). x is M III/(M III + M II) and is
normally between 0.2 and 0.33. m is the number of mol of cointercalated water per formula weight of compounds and is normally between 0.33 and 0.50. LDHs possess a well-defined layered
structure with unique properties such as adsorption capacity, anion
exchange capacity, and mobility of interlayer anions and water
molecules. Accordingly, they may be of great value for potential
applications as anion-exchange materials, adsorbents or ecological
materials (Cavani and Trifiro, 1991; Del Hoyo, 2007; Goh et al.,
2008; Manohara and Kamath, 2010; Meyn et al., 1990; TorresDorante et al., 2009; Vaccari, 1998). With consideration to overall
comparison of structures, compositions and performances of
LDHs, serpentine and some other silicate minerals, as well as catalytic properties of co-containing LDHs and co-containing materials
(Krylova et al., 2008; Zhang et al., 2008), this paper synthesized
Co–Al–CO3 LDHs(CAC-LDHs) by co-precipitation methods and systematically studied their phase compositions, structures, thermal
stability and friction performances.
Z.M. Bai et al. / Applied Clay Science 59–60 (2012) 36–41
2. Experimental and characterization methods
37
Table 1
lattice parameters of products synthesized with different Co/Al ratios.
2.1. Materials
Sample
a
b
c
Raw materials used for synthesis of CAC-LDHs include
Co(NO3)2·6H2O, Al(NO3)3·9H2O, NaOH and Na2CO3. All these materials are analytically pure. Deionized water is used to obtain
solutions.
(003) FWHM/°
d003/nm
d110/nm
a0/nm
c0/nm
Phase
0.346
0.759
0.153
0.307
2.277
LDHs
0.311
0.771
0.154
0.309
2.314
LDHs
0.293
0.767
0.151
0.302
2.300
LDHs + Co(OH)2
2.2. Synthesis of CAC-LDHs
A — Co/Al = 2/1, b — Co/Al = 3/1, c — Co/Al = 4/1. Three samples were prepared under
crystallization temperature of 120 °C and crystallization time of 5 h.
(003) FWHM is the peak width at half-height of diffraction peak (003);
A series of CAC-LDHs samples was synthesized by co-precipitation
methods (Feikneeht and Gerber, 1942; Gastuehe and Broo, 1967).
Solutions of three different Co:Al mol ratios, i.e., 2:1, 3:1 and 4:1
have been prepared as below.
Solution A was prepared by dissolving Mg and Al nitrate salts with
different mol concentration such as [Co(NO3 ) 2 ·6H2 O] 0.66 mol,
[Al(NO 3 ) 3 ·9H2 O] 0.34 mol for Co:Al = 2:1; [Co(NO 3 ) 2·6H 2 O]
0.75 mol, [Al(NO 3 ) 3 ·9H 2 O] 0.25 mol for Co:Al = 3: 1 and
[Co(NO3)2·6H2O] 0.80 mol, [Al(NO3)3·9H2O] 0.20 mol for Co:
Al = 4:1.
Solution B has sodium carbonate [Na2CO3: Co(NO3)2 · 6H2O = 1:1 mol ratio] dissolved in 20 mL of NaOH (2.25 mol). Both solutions A and B were added into a container simultaneously at a flow
rate of 8–10 mL/min.
Three samples having Co:Al mol ratio (2:1, 3:1 and 4:1) were
prepared under crystallization temperature of 120 °C and crystallization time of 5 h. The samples obtained are designated as a, b
and c. The XRD patterns and lattice parameters of CAC-LDHs prepared with different Co:Al mol ratio are shown in Fig. 1 and
Table 1.
Four samples having Co:Al mol ratio 3:1 were prepared under different temperatures(100 °C, 120 °C, 150 °C and 200 °C)for 5 h. The
XRD patterns of these samples are shown in Fig. 2, while their lattice
parameters are summarized in Table 2.
Six samples having Co:Al mol ratio 3:1 were prepared under different crystallization time (0.5 h, 1 h, 2 h, 3 h, 5 h and 7 h) and crystallization temperature of 120 °C. The lattice parameters of these
samples are summarized in Table 3.
Two samples having Co:Al mol ratio 3:1 were prepared in
water and mixture of water–ethanol (water/ethanol = 2/1, in volume) and under 120 °C for 5 h. The SEM of two samples is
shown in Figs. 3 and 4.
A lubrication oil (CD15W-40, with viscosity of 15.02 mm 2/s at
100 °C and 110.60 mm 2/s at 40 °C, viscosity index of 228 and open
flash-point temperature of 228˚C) was chosen for use as the base oil
in the tribological tests. The synthesized CAC-LDHs power (5 g) and
the base oil (1 L) were blended together at 75 °C through stirring
under high rotational speed (10,000 r/min) for 20 min. Then the uniformly dispersed and stable lubricating oil with CAC-LDHs power was
obtained.
Friction and wear experiments were carried out using a MR5-10A
four-ball friction tester. Steel balls are Cr15 steel having hardness of
Fig. 1. XRD patterns of products synthesized with different Co/Al ratios. a — Co/Al = 2/
1, b — Co/Al = 3/1, c — Co/Al = 4/1. Three samples were prepared under crystallization
temperature of 120 °C and crystallization time of 5 h.
Fig. 2. XRD patterns of products synthesized under different temperatures. a—100 °C, b
—120 °C, c—150 °C, d—200 °C. All of four samples are with Co/Al of 3:1 and crystallization time of 5 h.
2.3. Characterization of CAC-LDHs
All samples were characterized by powder X-ray diffraction (XRD)
using Model D-2 diffractometer (CuKα radiation, λ = 1⋅541 Å). Data
were collected over a 2θ range of 3–70° (step size of 0⋅02, scanning
rate of 8°/min). The Fourier transform infrared spectroscopy (FT-IR)
was recorded using the KBr pellet technique on a Vector22 spectrometer in the 4000–500 cm − 1 wave number range. The pellets were
prepared by weighing approximately 100 mg of KBr and 1 mg of the
sample. TG/DTA analysis of the sample was performed using TGA
(Model PCA-IA) in the temperature range from 25 to 800 °C with a
heating rate of 10 °C/min. N2 adsorption and desorption isotherms
of sample (was outgassed at 573 K for 4 h) were measured at 77.4 K
using an Quantachrome Instruments. Surface area was determined
from N2 adsorption data using the BET equation (Gregg and Sing,
1982). The morphological features of the samples were studied by
SEM (Model S4800).
2.4. Tribological properties of CAC-LDHs
38
Z.M. Bai et al. / Applied Clay Science 59–60 (2012) 36–41
Table 2
XRD parameters of products synthesized under different crystallization temperature.
Crystallization temperature/°C 100
120
150
200
(003)/°
d003/nm
d110/nm
a0/nm
Phase
0.444
0.782
0.154
0.309
LDHs
0.311
0.754
0.154
0.309
LDHs
Crystallinity/%
51.4
92.8
0.305
0.771
0.154
0.308
LDHs
+ Co(OH)2
88.5
0.257
0.763
0.150
0.310
LDHs
+ Co(OH)2
93.5
All of four samples are with Co/Al of 3:1 and crystallization time of 5 h.
(003) FWHM is the peak width at half-height of diffraction peak (003).
Crystallinity was determined by using software Jade on bases of XRD data.
59–61 HRC. Operation parameters of the tester are rotation speed of
1200 r/min, loading capacity of 392 N, and test duration of 30 min.
The power consumption of driving motor was measured using
Model 8705B power meter, whereas oil temperature was measured
using Model JM222 thermometer during both the gear friction test
and air compressor test.
3. Results and discussion
3.1. Structure and phase composition
3.1.1. Effect of Co:Al ratio
The XRD patterns and lattice parameters (Fig. 1 and Table 1) show
that the value for the (003) X-ray reflection (0.759–0.771 nm) agrees
thoroughly with synthetic hydrotalcite in the case of the carbonate
anion as the guest (Mascolo, 1986; Miyata, 1983).
In the samples having higher Co/Al mol ratios (4:1), synthesized
products contain both CAC-LDHs and Co(OH)2 crystal phase. For the
samples having lower Co/Al mol ratios(2:1–3:1), synthesized products contain CAC-LDHs only, and d003 increases from 0.759 to
0.771 nm with increasing the Co/Al mol ratios from 2:1 to 3:1, whereas (003)FWHM, which may reflect Crystallinity of LDHs, decreases with
increasing Co/Al ratios. In the samples having higher Co content, the
smaller size of Al 3+ (0.05 nm) as compared to Co 2+ (0.074 nm)
leads to significant increase of the d003 value. The results agree with
synthetic Mg–Al–CO3 LDHs (Sharma et al., 2008).
Fig. 3. SEM images of LDHs synthesized in water at (a) low magnification and (b) high
magnification. The sample was prepared with Co/Al of 3:1, under 120 °C, for 5 h, in
water.
3.1.2. Effect of crystallization temperature
It can be seen that only CAC-LDHs exist in products at crystallization temperatures of 100 °C and 120 °C(Fig. 2). But at 120 °C, crystallinity of CAC-LDHs is much higher and (003) FWHM is obviously lower
than that of products at 100 °C(Table 2). In addition, at 150 and
200 °C, a small amount of Co(OH)2 was present in products beside
LDHs and content of Co(OH)2 at 200 °C is much higher than that of
150 °C. Therefore, 120 °C was chosen as the optimum crystallization
temperature for preparing CAC-LDHs.
3.1.3. Effect of crystallization time
XRD data(Table 3) show that only CAC-LDHs may be produced at
crystallization time of 0.5–5 h, and (003) FWHM of CAC-LDHs
Table 3
XRD results of products generated at different crystallization time.
Crystallization time
0.5 h
1h
2h
3h
5h
7h
(003)/°
d003/nm
d110/nm
a0/nm
Phase
Crystallinity/%
0.732
0.773
0.154
0.308
LDHs
23.8
0.581
0.772
0.154
0.309
LDHs
56.5
0.563
0.771
0.154
0.308
LDHs
76.4
0.359
0.772
0.154
0.309
LDHs
88.6
0.311
0.771
0.154
0.309
LDHs
92.8
0.301
0.771
0.154
0.308
LDHs + Co(OH)2
93.1
All of six samples are with Co/Al of 3:1 and crystallization temperature of 120 °C.
(003) FWHM is the peak width at half-height of diffraction peak (003).
Fig. 4. SEM images of LDHs synthesized in mixture of water–ethanol at (a) low magnification and (b) high magnification. The sample was prepared with Co/Al of 3:1, under
120 °C, for 5 h, in mixture of water–ethanol (water/ethanol = 2/1, in volume).
Z.M. Bai et al. / Applied Clay Science 59–60 (2012) 36–41
39
decreases with extension of crystallization time. It can be seen that
crystallinity of CAC-LDHs increases with extension of crystallization
time. However, final products may include Co(OH)2 besides CACLDHs with the reaction time reached 7 h. Similar phenomenon that
the formation of CAC-LDHs was affected by aging time has been
reported earlier (Saber et al., 2005).
Following quantitative relation can be identified between crystallization time (h) and crystallinity (x) of products through matching:
2
x ¼ 100 ½1−expð−0:732 hÞ; R ¼ 0:988 :
3.1.4. Effect of media types
Test results show that CAC-LDHs crystals with perfect sheet
shapes have been produced in both of water media and water–ethanol media, but the sample prepared in water media was found having
larger disk diameter (200–300 nm, Fig. 3) as compared to samples
prepared in water–ethanol media (150–200 nm, Fig. 4).
Fig. 5. Infrared spectra of Co–Al–CO3 LDHs synthesized under optimized conditions.
The sample was prepared with Co/Al of 3:1, under 120 °C, for 5 h, in mixture of
water–ethanol (water/ethanol = 2/1, in volume).
3.2. Features of CAC-LDHs prepared under optimized conditions
On the basis of the above results on various synthetic parameters,
water–ethanol solution with Co/Al mol ratio of 3:1, crystallization
temperature of 120 °C and crystallization time of 5 h were chosen as
optimum synthetic parameters to prepare CAC-LDHs. The sample
prepared using these optimized synthetic conditions was observed
to have perfect crystals with hexagonal lamella structures, disk diameter of 150–200 nm and thickness of approximately 20 nm,
a0 = b0 = 0.309 nm, c0 = 2.314 nm, d-spacing = 0.77 nm and gallery
height = 0.29nm.
3.2.1. Infrared spectrum characteristics
The FT-IR spectra of CAC-LDHs prepared with optimized synthetic
conditions are shown in Fig. 5. The sharp band observed at about
3521 cm − 1 is assigned to O\H stretching (νO\H) due to the presence of hydroxyl as well as both adsorbed and interlayer water
(Iglesias et al., 2005). The shoulder observed between 2800 cm − 1
and 3200 cm − 1 can be assigned to hydrogen bonds between water
and CO32− (Labajos et al., 1992). The bending mode H\O\H from
H2O was observed at 1638 cm − 1, thus confirming the presence of
water in the interlayer space. The sharp band observed at about
1363 cm− 1 is attributed to the ν3 asymmetric stretching of the CO32−.
When compared with free CO32−(ν3 = 1415 cm− 1) (HernandezMoreno et al., 1985), the ν3 mode observed in CAC-LDHs appears downshifted by 52 cm− 1 due to interaction of these anions with water molecules through hydrogen bonds. However, these interactions are not
strong enough to distort the CO32− anions from their D3h free molecule
symmetry. The shoulder observed at 854 cm− 1 is assigned to the ν2
bending mode of the carbonate anion, whereas the FT-IR modes
below 800 cm− 1can be attributed to the Co(Al)\OH vibrations.
at ∼ 265 °C due to decarbonation and the third peak at ∼ 315 °C due
to dehydroxyl. The TG also showed three clearly endothermic weight
losses, the first weight loss is between 25 °C and 215 °C, the second is
between 215 °C and 265 °C and the third is >265 °C.
3.2.3. Specific surface area and pore volume
CAC-LDHs synthesized in this paper have a large pore volume
(0.14 cm 3/g) and total specific surface area (TSSA, 97 m 2/g),and
about 72% of the TSSA is external specific surface area (70 m 2/g).
The TSSA of this sample is far higher than that of serpentine powder
(TSSA, 45 m 2/g) having an average diameter of 500 nm and could
been used as lubricating oil additive.
3.3. Friction performances of CAC-LDHs
3.3.1. Four-ball friction tests
Fig. 7 shows the variation of friction coefficient for oil with and
without CAC-LDHs. The friction coefficient of base oil progressively
increases with the extension of running time, and the largest friction
coefficient is 0.83, the average friction coefficient in 0.073 within
30 min. But by contrast, the friction coefficient of with CAC-LDHs
evenly decreases with the extension of running time and the average
friction coefficient in 0.037 (within 30 min), decreases the friction coefficient by 49% as compared with base oils. In addition, wear scar
3.2.2. Thermal analysis
Fig. 6 shows a typical DTA/TG thermogram of the CAC-LDHs. The
DTA curve shows three endothermic peaks, the first broad peak at
∼ 215 °C due to dehydration of interlayer water, the second peak
Table 4
Comparison of wear scar diameters of steel balls in four-ball friction tests.
Sample
BO
CAC
Wear scar diameters of
balls (mm)
Ball 1
Ball 2
Ball 3
0.489
0.306
0.478
0.315
0.454
0.331
BO—without LDHs; CAC—with LDHs.
Average diameter
of wear scar (mm)
Reduction of
diameters of
wear scar (%)
0.474
0.317
33.1
Fig. 6. TG-DTA curves of Co–Al–CO3 LDHs synthesized under optimized condition. The
sample was prepared with Co/Al of 3:1, under 120 °C, for 5 h, in mixture of water–ethanol (water/ethanol = 2/1, in volume).
40
Z.M. Bai et al. / Applied Clay Science 59–60 (2012) 36–41
45
Oil Temperature/ć
40
35
30
BO
CAC
25
20
0
60
120
180
240
300
360
420
480
540
600
Time/min
Fig. 7. Changes of friction coefficient in four-ball friction test. BO—without LDHs; CAC—
with LDHs.
diameter of steel balls in system with CAC-LDHs (0.317 mm) decreased by 33.1% as compared with base oils(0.474 mm) (Table 4).
The phenomena that CAC-LDHs could significantly reduce friction coefficient and wear of friction pairs are agree with that of serpentine(trioctahedral hydrous phyllosicates based on 1:1 layer structures)(Qi
et al., 2011; Yu et al., 2010).
3.3.2. Gear tests and air compressor tests
Figs. 8, 9 and 10 show the variation of power consumption of driving motor and temperature of lubrication oil with and without CACLDHs during gear tests and air compressor tests. With LDHs added,
average power consumption of driving motor can be reduced 7.0%
(gear tests) and 4.8% (air compressor tests), whereas temperature
of lubrication oil can be reduced 7.7% (gear tests) and 7.4% (air compressor tests). In addition, with LDHs added, power consumption of
driving motor and temperature of lubrication oil are more stable as
compared with the base oil (without LDHs).
Above tests indicate that CAC-LDHs can significantly reduce friction coefficient, wear of friction pairs, temperature of lubrication oil
and power consumption of driving motor; this is similar to that
which is observed for Iayer structure minerals such as serpentine(Jin,
2010; Qi et al., 2011; Shi et al., 2007; Xu et al., 2009; Yang and Bai,
260
Fig. 9. Temperature of lubrication oil in tester as a function of time. BO—without LDHs;
CAC—with LDHs.
2010; Yang et al., 2005; Yu et al., 2010; Zhang et al., 2009). Both
LDHs and serpentine have layer structures and a platelet morphology
with the layers connected by weak molecular bond and/or hydrogen
bonds, which is easy to slide among layers under shearing force. LDHs
have large specific surface area and unsaturated bond, which could
help them to stick to surface of friction pair to form physical protective coating. Metallic irons(Mg 2+, Co 2+ and Al 3+) of LDHs may
have metathesis with iron atoms of friction pairs and generate protective coating on the friction pairs surface (Yu et al., 2010), whereas anions (OH −,CO32−) of LDHs could lead to oxidation of iron atoms on
friction pair surface and producing oxide coating with high hardness
(Jin, 2010). All of these may be the reasons that CAC-LDHs could reduce friction coefficient and wear of friction pairs as well as temperature of lubrication oil and power consumption of driving motor.
4. Conclusions
Co-precipitation method has been employed to synthesize Co–Al–
CO3 LDHs (CAC-LDHs). Our experiments showed that synthesized
LDHs products have perfect crystals with hexagonal lamella structures. Most of these crystals have diameters around 150–200 nm
and thickness of 20 nm. With a0 = b0 = 0.309 nm, c0 = 2.314 nm,
d-spcing = 0.77 nm and gallery height = 0.29 nm, these structures
can be categorized into hexagonal system. Total specific surface area
255
Consumption/Watt
250
245
240
235
230
BO
225
CAC
220
215
0
60
120
180
240
300
360
420
480
540
600
Time/min
Fig. 8. Power consumption of driving motor as a function of time.BO—without LDHs;
CAC—with LDHs.
Fig. 10. Power consumption of driving motor as a function of time. BO—without LDHs;
CAC—with LDHs.
Z.M. Bai et al. / Applied Clay Science 59–60 (2012) 36–41
is 97 m 2/g and pore volume is 0.14 cm 3/g. Optimal conditions for
preparation of LDHs are as follows: solution of water–ethanol mixture shall be used as media, Co/Al mol ratio shall be 3:1, crystallization temperature shall be 120 °C and crystallization time shall be
5 h. CAC-LDHs can significantly reduce friction coefficient and wear
of frication pairs. At the same time, they can reduce temperature of
lubrication oil (7.4–7.7%) and power consumption of driving motor
(4.8–7.0%). These favorable features can make them one of the innovative lubrication and anti-frictional materials with extensive potential applications.
Acknowledgment
This project was sponsored by the National Natural Science Foundation of China (51044011) and National Laboratory of Mineral
Materials.
References
Cavani, F., Trifiro, F., 1991. Hydrotalcite-type anionic clays: preparation, properties and
applications. Catalysis Today 11 (2), 173–301.
Del Hoyo, C., 2007. Layered double hydroxides and human health: an overview. Applied Clay Science 36, 103–121.
Feikneeht, W., Gerber, M., 1942. Double hydroxides and basieal double salts. II Mixed
precipitates from calcium–aluminum salts solutions. III Magnesium–aluminum
double hydroxides. Helvetica Chimica Acta 25, 106–137.
Gastuehe, M.C., Broo, G., 1967. Mixed Mg–Al hydroxides prep. and characterization of
compounds. Clay Minerals 7, 177–192.
Goh, K.H., Lim, T.T., Dong, Z.L., 2008. Application of layered double hydroxides for removal of oxyanions: a review. Water Research 42, 1343–1368.
Gregg, S.J., Sing, K.S.W., 1982. Adsorption, Surface Area and Porosity, 2nd ed. Academic
Press, New York.
Hernandez-Moreno, M.J., Ulibarri, M.A., Rendom, J.L., et al., 1985. IR characteristics of
hydrotalcite-like compounds. Physics and Chemistry of Minerals 12, 34–38.
Iglesias, A.H., Ferreira, O.P., Gouveia, D.X., et al., 2005. Structural and thermal properties of
Co–Cu–Fe hydrotalcite-like compounds. Journal of Solid State Chemistry 178,
142–152.
Jin, Y.S., 2010. The effect of internal oxidation from serpentine on generating reconditioning layer on worn ferrous metal surfaces. China Surface Engineering 23, 45–50.
Krylova, M.V., Kulikov, A.B., Knyazeva, M.I., 2008. Cobalt-containing catalysts made
from layered double hydroxides for synthesis of hydrocarbons from carbon monoxide and hydrogen. Chemistry and Technology of Fuels and Oils 44 (5), 339–343.
41
Labajos, F.M., Rives, V., Ulibarri, M.A., 1992. Effect of hydrothermal and thermal treatments on the physicochemical properties of Mg-Al hydrotalcite-like materials. J.
Mater. Sci. 27 (6), 1546–1552.
Li, G.J., Bai, Z.M., Huang, W.J., et al., 2008. Research of serpentine powder surface modification. Bulletin of the Chinese Ceramic Society 27 (6), 1091–1096.
Li, P., 2007.Hydrothermal synthesis and fabrication properties of serpentine micropowder(in Chinese, dissertation).Beijing: China University of Geosciences.
Manohara, G.V., Kamath, V.P., 2010. Synthesis and structure refinement of layered double hydroxides of Co, Mg and Ni with Ga. Bulletin of Materials Science 33 (3),
325–331.
Mascolo, G., 1986. Thermal stability of lithium aluminium hydroxy salts. Thermochimica Acta 102 (15), 67–73.
Meyn, M., Beneke, K., Lagaly, G., 1990. Anion-exchange reactions of layered double hydroxides. Inorganic Chemistry 29 (26), 5201–5207.
Miyata, S., 1983. Anion-exchange properties of hydrotalcite-like compounds. Clays and
Clay Minerals 31 (4), 305–311.
Qi, X.W., Jia, Z.N., Yang, Y.L., et al., 2011. Characterization and auto-restoration mechanism of nanoscale serpentine powder as lubricating oil additive under high temperature. Tribology International 44, 805–810.
Saber, O., Hatano, B., Tagaya, H., 2005. Preparation of new layered double hydroxide, Co-Ti LDH. Journal of Inclusion Phenomena and Macrocyclic Chemistry 51,
17–25.
Sharma, U., Tyagi, B., Jasra, R.V., 2008. Synthesis and characterization of Mg–Al–CO3
layered double hydroxide for CO2 adsorption. Industrial and Engineering Chemistry Research 47, 9588–9595.
Shi, P.J., Yu, H.L., Zhao, Y., et al., 2007. Effects of in-situ tribochemical treatment on mechanical property and tribological behavior of 45 steel. Transactions of Materials
and Heat Treatment 28 (2), 113–117.
Torres-Dorante, L.O., Lammel, J., Kuhlmann, H., 2009. Use of a layered double hydroxide
(LDH) to buffer nitrate in soil: long-term nitrate exchange properties under cropping and fallow conditions. Plant and Soil 315 (1–2), 257–272.
Vaccari, A., 1998. Preparation and catalytic properties of cationic and anionic clays. Catalysis Today 41 (1–3), 53–71.
Xu, Y., Yu, H.L., Zhao, Y., et al., 2009. Study on tribological properties of stratified silicate
self-repair materials. China Surface Engineering 22 (3), 58–61.
Yang, H., LI, S.H., Jin, Y.S., 2005. Study on tribological behavior of Mg6Si4O(10)(OH)8 additive package with steel tribo-pair. Tribology 25, 308–311.
Yang, Q.M., Bai, Z.M., 2010. The material characteristic and tribological intervention behaviors of hyper-fine serpentine powder and its industrial application. Lubrication
Engineering 35 (9), 98–102.
Yu, H.L., Xu, Y., Shi, P.J., et al., 2010. Tribological behaviors of surface-coated serpentine
ultrafine powders as lubricant additive. Tribology International 43, 667–675.
Zhang, B., Xu, B.S., Xu, Y., et al., 2009. Effect of magnesium silicate hydroxide on the friction behavior of ductile cast iron pair and the self-repairing performance. Journal
of the Chinese Ceramic Society 37 (4), 492–495.
Zhang, F.Z., Xiang, X., Li, F., et al., 2008. Layered double hydroxides as catalytic materials: recent development. Catalysis Surveys from Asia 12 (4), 253–265.