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2018 Vol. 23, No. 2
Published: 2018-04-20
Theoretical Research
119
Effects of sintering aids Al
2
O
3
and Y
2
O
3
on the lithium ion conductivity of solid lithium ion electrolyte LLZO
LI Jian, JIANG Yixiong, ZHOU Hongming
The garnet-type ceramic electrolyte Li
7
La
3
Zr
2
O
12
(LLZO) with composition of
x
Al
2
O
3
-Li
7
La
3
Zr
2
O
12
(
x
=0-0.4) and
x
Y
2
O
3
-Li
7
La
3
Zr
2
O
12
(
x
=0, 0.1, 0.2, 0.3 and0.4) were synthesized by adding Al
2
O
3
and Y
2
O
3
as sintering aids and using Li
2
CO
3
, La
2
O
3
and ZrO
2
as raw materials. The effects of the contents of sintering aids Al
2
O
3
and Y
2
O
3
on the lithium ion conductivity of solid lithium ion electrolyte LLZO were studied. The results reveal that two kinds of sintering aids both can stabilize the cubic phase of garnet structure LLZO after sintered at 1 500 ℃ for 15 h. The LaAlO
3
impurity phase is produced when Al
2
O
3
is over added. The Li
2
ZrO
3
and YO
1.458
impurity phases are produced when Y
2
O
3
is over added. Among these samples,0.2Y
2
O
3
-LLZO can stabilize the cubic phase from 1 100 ℃ to 1 200 ℃ and do not decompose when sintering at 1 150 ℃ for 27 h。The density of LLZO and the conductivity of lithium ion increase first and then decrease with increasing the content of sintering aids. The optimum additions of Al
2
O
3
and Y
2
O
3
are 0.2 and 0.3, respectively. The density and ionic conductivity of 0.2Al
2
O
3
-LLZO are 94% and 1.78×10
-4
S/cm, respectively. The density and ionic conductivity of 0.3Y
2
O
3
-Li
7
La
3
Zr
2
O
12
are 96% and 5.23×10
-4
S/cm, respectively.
2018 Vol. 23 (2): 119-123 [
Abstract
] (
310
)
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(253 KB) (
814
)
Engineering and Technology
124
Microstructure and erosion resistance of nanostructured WC-10Co4Cr coating sprayed by HVOF
ZHOU Xialiang, CHEN Xiaoming, WU Yanming, ZHAO Jian, LIU Wei, MAO Pengzhan, WANG Lirong
To improve the slurry erosion resistance of turbine surface, nano-structured and micro-structured WC- 10Co4Cr coatings were prepared on stainless steel (0Cr13Ni4Mo) surface by HVOF. Microstructure of powders and coatings with different structure were characterized by scanning electron microscopy (SEM). The micro-hardness, bonding strength and erosion resistance were compared. Erosion failure mechanism in the sandy stream was analyzed as well. The results show that the microstructure of nano-structured WC-10Co4Cr coating prepared by HOVF is dense. Its microhardness and bond strength are higher than that of conventional coating. As well, it is found that nano-structured coating exhibits lower erosion mass loss than that of micro-structure coating. Nano-structure coating has finer grains, higher microhardness and toughness, and better micro-cutting resistance and anti-fatigue spalling properties, and can enhance the slurry erosion resistance of the coating.
2018 Vol. 23 (2): 124-129 [
Abstract
] (
364
)
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561
)
130
Synthesis and characterization of CoFe
2
O
4
/BaTiO
3
multiferroic composites
WANG Jin, SU Yuchang, TAN Jiang, ZHANG Jing, REBIGULI·Tursun, YU Qiushan, ZHAO Le
The CoFe
2
O
4
/BaTiO
3
composite powder material was prepared by the combination of ferromagnetic cobalt ferrite and ferroelectric barium titanate by sol-gel method. The phase composition, molecular structure, micro- morphology, magnetic properties of the composite powder and ferroelectric properties of the sintered body were analyzed and characterized by XRD, infrared spectrometer(IR), SEM, TEM, vibrating sample magnetometer(VSM) and ferroelectric analyzer. The results show that the CoFe
2
O
4
/BaTiO
3
composite powder prepared by sol-gel method is composed of cobalt ferrite and barium titanate phases. The morphology of the powder is spherical, and the particle size is uniform. The grain size increases with the increase of synthetic temperature. The magnetic properties of the material increase with increasing the ratio of cobalt ferrite. When the molar ratio of cobalt ferrite and barium titanate is
n
(CoFe
2
O
4
):
n
(BaTiO
3
)=2:1, the saturation magnetization intensity of the composite is 40.01 (A∙m
2
)/kg, and the residual magnetization intensity is 20.59 (A∙m
2
)/kg. Meanwhile, a ceramic was prepared using this powder. The electric field is 4.12×10
6
V/m, and the remanent polarization is 0.30 C/m
2
. It has good ferromagnetic and ferroelectric properties at the same time.
2018 Vol. 23 (2): 130-136 [
Abstract
] (
361
)
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1695
)
137
Effects of HfC addition on plasma flame flow ablation resistance of molybdenum-tungsten alloys and its mechanism analysis
YANG Lilin, ZHANG Qifu, HE Zhiyong, LI Xiaogang
The plasma ablation system combined with scanning electron microscopy (SEM) in this work were used to investigate the effects of different amounts of HfC particles on ablation performance and ablation morphology of sintered and rolled molybdenum-tungsten (Mo-W) alloys. Also, the high temperature ablation mechanism of the alloys was further discussed. The results show that the addition of HfC can significantly improve the ablation resistance of the alloys, including sintered and rolled alloys. The ablation resistance of the rolled alloys is obviously better than that of the sintered alloys due to the formation of lamellar structure and eliminating the internal defects (such as pores and impurity) after the rolled treatment. Compared with oxyacetylene ablation experiment, the plasma ablation experiment has protective gas along with strong impact force during ablation process. The ablation process is mainly physical and mechanical ablation. HfC doping mechanism is mainly because of its high melting point as a stagnation point. On the other hand, a small amount of HfO
2
film formed on the substrate also has protection effect. As a result, high temperature ablation property of Mo-W alloys is increased.
2018 Vol. 23 (2): 137-146 [
Abstract
] (
373
)
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980
)
147
Effects of expanded graphite on the current carrying tribological properties of phosphor-bronze fiber brush
LUO Bo, JING Guiru, LI Changjiang, ZHANG Lei
A fiber brush was prepared by rolling the fiber bundle with expanded graphite paper using phosphor-bronze fibers with diameter of 50 μm as the main material and expanded graphite paper as the lubricant. The effects of expanded graphite content on the electric contact property and current carrying tribological properties of the fiber brush were studied. The results show that, a three-dimensional brush structure with uniform dispersion of fibers was constructed through bending the phosphor-bronze fibers, which leads to a lower elastic constant and appropriate compression strength of the fiber brush. The bent phosphor-bronze fiber brush, compared to the unbent phosphor-bronze fiber brush with the same packing fraction of fiber (17.5%), possesses slightly higher compressive strength (2.69 MPa vs 2.62 MPa) and lower elastic constants (149.5 N/mm vs 428.8 N/mm). The friction and wear properties of the brushes increase while the electrical contact property decreases. With the content of expanded graphite increasing from 6.2% to 29.1%, the friction coefficient decreases from 0.67 to 0.25, and the contact voltage drop increases from 244.86 mV to 427.81 mV. Otherwise, the asymmetric wear behavior of the phosphor-bronze fiber brush can be suppressed by the lubricating effect of expanded graphite. The wear rates of the negative and positive brush without expanded graphite are 5.83×10
-9
m/m and 1.12×10
-8
m/m respectively. As the content of expanded graphite increases to 29.1%, the wear rate of the negative and positive brush decrease to 0.44×10
-9
m/m and 0.53×10
-9
m/m respectively.
2018 Vol. 23 (2): 147-156 [
Abstract
] (
389
)
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(1 KB)
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(1784 KB) (
736
)
157
Effects of Cd element on the deposition process of Al-4Cu alloy
GONG Zhu, ZHENG Ziqiao
The effects of trace addition of Cd elements on Al-Cu alloy were investigated by the micro-hardness test, tensile test and transmission electron observation (TEM). The results indicate that due to the strong interaction between Cd elements and vacancies, when the alloys are aged at 100 ℃, the additon of trace Cd inhibits the formation of GP zones, and it further decreases the aging reponse rate, the peak-aging hardness and tensile strength. When the alloys are aged at 150 ℃, the Cd-rich particles in Al-Cu-Cd alloy will act as heterogeneous nucleation position of θ′ phases and then promote the precipitation of θ′ phases is (110)
Cd
‖(001)
Al
‖(001)
θ
, which improves the tensile strength of the alloy. The orientation relationship of Cd particles θ′ phases and Al-matrix.
2018 Vol. 23 (2): 157-166 [
Abstract
] (
249
)
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(702 KB) (
1080
)
167
Microstructure and mechanical properties of 2.5D curved shallow-crossing linking SiC
f
/SiC composites fabricated by chemical vapor infiltration
LI Yue, ZHANG Ruiqian, YANG Ping, CHEN Zhaoke, HE Zongbei, XIONG Xiang
The tubular SiC
f
/SiC composite materials were prepared by depositing SiC-PyC-SiC multi-interlayers on the SiC fibers with 2.5D curved shallow-crossing linking structure densified with SiC matrix using CH
3
SiCl
3
-H
2
-Ar system by chemical vapor infiltration (CVI). The phase composition, microstructure, axial compression, radial crushing and circumferential tension and fracture morphology of SiC
f
/SiC composites were investigated. The results show that SiC
f
/SiC composites are mainly composed of SiC fiber, SiC-PyC-SiC multi-interlayers and SiC matrix. In the SiC-PyC-SiC multi-interlayers, the thickness of PyC interlayers is 700-800 nm, the thickness of SiC interface is 400-500 nm, and SiC matrix is mainly β-SiC phase. After densification, the density of SiC
f
/SiC composites is 2.50-2.58 g/cm
3
, and the porosity is 7.70%-9.10%. The axial compressive strength of SiC
f
/SiC composites is 53.2 MPa, and the radial crushing strength is 38.18 MPa. Compression is expressed as a shear failure in the 45° direction with the horizontal plane
2018 Vol. 23 (2): 167-171 [
Abstract
] (
420
)
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(1 KB)
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(713 KB) (
1211
)
172
Microstructur and mechanical properties of the friction stir welded joint of 7020 aluminum alloy
CHEN Xiangrong, ZHENG Ziqiao
The microstructure and mechanical properties of friction stir welded 7020-T6 alloy were investigated by micro-hardness test, tensile mechanical properties test, metangraphic microscope, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the hardness distribution appears as the W-shaped profile in alloy weld zone and reaches to minimum in HMAZ/HAZ. The tensile strength, yield strength, elongation and welding coefficient of the welded joint are 352 MPa, 223 MPa, 9.8% and 86.9%, respectively. The grain structure shows significant difference in the welded zone. The fine and dispersive precipitates of CP zone and η° phase formed after artificial aging (90 ℃/8 h+135 ℃/16 h) in base metal are dissolved during the process of friction stir weld and re- precipitate later, but the size and density of precipitates in welded joint are much smaller than base metal.
2018 Vol. 23 (2): 172-179 [
Abstract
] (
390
)
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(1 KB)
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(1601 KB) (
980
)
180
Synthesis, magnetic and microwave absorption properties of extremely Ni-C core-shell nanoparticles
KUANG Daitao, WEN Xiang, LIANG Bingbing, HOU Lizhen, MA Songshan, WANG Shiliang
Ultra-small Ni-C core-shell nanoparticles were synthesized by the metal organic chemical vapor deposition (MOCVD) using Ni(acac)
2
as precursor. The structure and magnetic properties of the as-synthesized nanoparticles were characterized by XRD, Raman spectroscopy, TEM and Physical Property Measurement System respectively. The Ni nanocores have an average diameter of 13 nm, and are encapsulated by C shells with the thickness of 1-3 nm. The Ni-C core-shell nanoparticles have a saturation magnetic moment of 24.5 emu/g, coercivity of 65.5 Oe which is much smaller than the corresponding values of bulk Ni and Ni-C core-shell nanoparticles which are 20 nm in diameters. In the microwave absorption tests, a low reflection loss (
RL
) of -48.7 dB and a large effective bandwidth (frequency range for
RL
≤-10 dB) of 7.4 GHz are obtained from the composites of small Ni-C core-shell nanoparticles and paraffin. This suggests that the as-synthesized ultra-small Co-C core-shell nanoparticles have a high potential as the microwave- absorbing materials.
2018 Vol. 23 (2): 180-185 [
Abstract
] (
271
)
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947
)
186
Deposition of MoS
x
self-lubricating coatings by cathodic arc plating with ion source
LI Zhujun, LIU Yifei, TIAN Canxin, YANG Bing, FU Dejun, SU Fenghua
MoS
x
self-lubricating coatings was deposited on crystal Si and cemented carbide substrates using Ar, H
2
S and metal molybdenum as S and Mo source by arc ion plating, by hollow cathode arc ion source. The effects of H
2
S flow rate on microstructure and mechanical properties of the coatings were systemically investigated. The results show that the H
2
S flow rate has a significant effect on crystalline structure, micro-hardness and friction coefficient of MoS
x
coating. With the increase of H
2
S flow rate, the grain size of Mo decreases while the content of MoS
x
increases in the coatings. The microhardness and average friction coefficients decrease with increasing the H
2
S flow rate. The average friction coefficients are lower than 0.35 (mating cemented carbide). The H
2
S can be used for MoS
x
self-lubricating coating deposition. The structure of MoS
x
coatings deposited by arc ion plating is Mo nanocrystalline embedded in MoS, MoS
2
amorphous phase matrix.
2018 Vol. 23 (2): 186-191 [
Abstract
] (
286
)
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(1 KB)
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(501 KB) (
526
)
192
Microstructure and properties of TiCN-Mo coatings prepared by reactive plasma spraying
NI Pan, NIU Jinghui, LIU Hongbing, ZHANG Haifeng, MENG Hailong, JIANG Dehua, GONG Yue, SHAO Lin
Three types of TiCN-Mo coatings with different Mo contents were deposited on steel substrate surface by reactive plasma spraying. The phase composition and microstructures of as-sprayed coatings were investigated by XRD, SEM and EDS. A Vickers microhardness test was used to measure the microhardness and indentation fractures of the coatings. In addition, a statistics method of Weibull distribution was used to examine the microhardness scattering. The results show that all coatings consist of TiC
0.7
N
0.3
, TiN, Mo, minor Ti
2
O and molybdenum oxides. Metal Mo in white color is evenly distributed around TiCN to form a dense microstructure, which presents an alternately stacked characteristic. The Weibull distribution of the microhardness of three coatings is dominated by apparent scattering. Compared to the monolithic TiCN coatings, the as-sprayed coating with 10% Mo displays a relatively low scattering characteristic of Vickers microhardness and a dense microstructure as well as high indention toughness and strength.
2018 Vol. 23 (2): 192-198 [
Abstract
] (
385
)
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(1 KB)
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(639 KB) (
463
)
199
Effects of sintering aids Al
2
O
3
and Y
2
O
3
on the lithium ion conductivity of solid lithium ion electrolyte LLZO
LI Jian, JIANG Yixiong, ZHOU Hongming
The garnet-type ceramic electrolyte Li
7
La
3
Zr
2
O
12
(LLZO) with composition of
x
Al
2
O
3
-Li
7
La
3
Zr
2
O
12
(
x
=0-0.4) and
x
Y
2
O
3
-Li
7
La
3
Zr
2
O
12
(
x
=0, 0.1, 0.2, 0.3 and0.4) were synthesized by adding Al
2
O
3
and Y
2
O
3
as sintering aids and using Li
2
CO
3
, La
2
O
3
and ZrO
2
as raw materials. The effects of the contents of sintering aids Al
2
O
3
and Y
2
O
3
on the lithium ion conductivity of solid lithium ion electrolyte LLZO were studied. The results reveal that two kinds of sintering aids both can stabilize the cubic phase of garnet structure LLZO after sintered at 1 500 ℃ for 15 h. The LaAlO
3
impurity phase is produced when Al
2
O
3
is over added. The Li
2
ZrO
3
and YO
1.458
impurity phases are produced when Y
2
O
3
is over added. Among these samples,0.2Y
2
O
3
-LLZO can stabilize the cubic phase from 1 100 ℃ to 1 200 ℃ and do not decompose when sintering at 1 150 ℃ for 27 h。The density of LLZO and the conductivity of lithium ion increase first and then decrease with increasing the content of sintering aids. The optimum additions of Al
2
O
3
and Y
2
O
3
are 0.2 and 0.3, respectively. The density and ionic conductivity of 0.2Al
2
O
3
-LLZO are 94% and 1.78×10
-4
S/cm, respectively. The density and ionic conductivity of 0.3Y
2
O
3
-Li
7
La
3
Zr
2
O
12
are 96% and 5.23×10
-4
S/cm, respectively.
2018 Vol. 23 (2): 199-205 [
Abstract
] (
295
)
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(1 KB)
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(612 KB) (
1442
)
206
Controllable preparation of three dimensional micro-nano hierarchical structure NiO supercapacitor electrode material
YANG Hongzhi, ZOU Jianpeng, YI Chenqi, LENG Xian
NiO hollow microspheres with micro-nano hierarchical structure were synthesized using lysine as the structure regulator, nickel chloride and ammonia as raw materials through hydrothermal synthesis and calcination method. The microstructure and phase composition of NiO materials were characterized by scanning electronic microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and other detection methods. The results show that the prepared hierarchical NiO hollow microspheres with different sizes are well distributed, and the particle size is about 2-3 μm, which is stacked by of many NiO nanosheets. The length of the NiO flakes with clear edges is about 400-600 nm, while the thickness is only about 40-50 nm. Excellent dispersibility and spherical morphology of NiO microspheres can be obtained with addition of 0.6 g lysine at the reaction temperature of 40 ℃ as well as the hydrothermal time of 6 h. In addition, the obtained NiO sphere is hollow, with many flakes stacked and crossed to form a hierarchical structure. Such a unique structure can provide high porosity and specific surface area as well as open channels, all of which are beneficial to the diffusion and migration of both electrolyte ions and electrons. As working electrode, the specific capacitance of the prepared hierarchical NiO hollow microspheres can reach 1 340 F/g in the current density of 1 A/g using the three electrode system and after 1 000 cycles, and the capacity retention rate is 96.5%, showing superior electrochemical performance.
2018 Vol. 23 (2): 206-216 [
Abstract
] (
353
)
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(1 KB)
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(1685 KB) (
761
)
217
Properties of Cr
2
O
3
coating sprayed by high enthalpy plasma on 40Cr Steel
FANG Yong, FU Li, CHEN Xiaoming, LIU Wei, ZHAO Jian, MENG Jinbo
The Cr
2
O
3
coatings were sprayed by SQC-100 high enthalpy plasma spray on the surface of 40Cr steel for piston rod of hoist. The microstructure, micro-hardness, porosity, bonding strength, anti-wear performance and electrochemical performance were characterized. The results show that, the porosity of Cr
2
O
3
coating obtained by high enthalpy plasma spraying is 0.81%, the average microhardness (HV
0.2
) is 1 310.3, and the average bonding strength is 60.6 MPa. Friction and wear experiment show that, the mass loss of the Cr
2
O
3
coating is only 0.001 3 g, the mass loss of the 40Cr steel is 0.101 8 g. The anti-wear property of the coating is 78 times to the stainless steel matrix. The wear mechanism of Cr
2
O
3
coating is abrasive wear and adhesive wear. The Cr
2
O
3
coating has stronger electrochemical corrosion resistance than the matrix. The Cr
2
O
3
coatings sprayed by plasma have a good application prospect.
2018 Vol. 23 (2): 217-221 [
Abstract
] (
278
)
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831
)
222
Effects of Cu content on friction and wear behavior of (Ti-8Si)-
x
Cu alloy
ZHAO Qian, XU Xiaojing, RU Jinming, SHI Xiaodong, WANG Ya
(Ti-8Si)-
x
Cu (
x
=0, 5, 10 and 20%) alloy were prepared by powder metallurgy method using Ti, Si and Cu powder as raw materials. The effects of Cu content on the hardness and friction and wear properties at room temperature of Ti-8Si alloy were studied through hardness testing, room temperature dry sliding friction test and observation and analysis of the friction surface morphology and element composition. The results show that, adding Cu powder can improve the hardness of Ti-8Si alloy. The hardness of (Ti-8Si)-5Cu alloy is the highest, HV reaches 1 434.4, which is 40.4% higher than that of Ti-8Si alloy (1 021.5). The surface hardness of (Ti-8Si)-10Cu is almost equal to that of (Ti-8Si)-20Cu alloy, and HV is 1 180.9 and 1 171.9 respectively. The friction coefficient of the alloy increases from 0.36 to 0.6 by adding Cu. However, adding the appropriate amount of Cu can obviously improve the wear resistance of the alloy, and the volume wear volume (0.014 3 mm
3
) of 95 (Ti-8Si)-5Cu alloy is about half of the Ti-8Si alloy (0.026 2 mm
3
). The wear volume of (Ti-8Si)-10Cu alloy is reduced by 13.7% than Ti-8Si alloy. The wear volume of the (Ti-8Si)-20Cu alloy increases sharply to 2.5 times that of the Ti-8Si alloy. The wear forms of 95 (Ti-8Si)-5Cu alloy are mainly abrasive wear and adhesive wear, accompanied by slight oxidation wear. The other 3 alloys are mainly fatigue wear and oxidation wear, with a certain degree of abrasive wear and adhesive wear.
2018 Vol. 23 (2): 222-228 [
Abstract
] (
354
)
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(1 KB)
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(587 KB) (
605
)
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