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2022 Vol. 27, No. 6
Published: 2022-12-15
Engineering and Technology
Engineering and Technology
569
Mechanical and tribological properties of GB/GF/PA1212 fabricated by selective laser sintering
WU Ting, WU Hong, WEN Jiebin
DOI: 10.19976/j.cnki.43-1448/TF.2022032
GB/GF/PA1212 composites were prepared by selective laser sintering (SLS) using of a mechanically blended mixture of polyamide (PA) 1212, glass fiber (GF) and glass beads (GB), where the GB and GF were acting as reinforcements. The tensile and tribological properties of SLS sintered parts were tested by a universal mechanical testing machine and a friction and wear tester to explore the influence of GB content on the properties of the composites, respectively. The results show that the presence of GB fillers at an appropriate proportion can improve the tensile properties and wear resistance of the composites. Especially, it can significantly improve the wear resistance. When the mass fraction of GB and GF is 40% and 10% respectively, the friction coefficient and wear rate of the composite are the lowest, which are 0.23 and 1.1×10
-3
mm
3
/(N∙m) respectively.
2022 Vol. 27 (6): 569-578 [
Abstract
] (
1179
)
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(826 KB) (
1170
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579
Microstructure and mechanical properties of plasma activated sintered Ta-2Ti-
x
TiC composites
ZHANG Jian, JIA Hao, MA Shuai, ZHANG Shiquan, GE Shuai, LUO Guoqiang, SHEN Qiang
DOI: 10.19976/j.cnki.43-1448/TF.2022063
Ta-2Ti-
x
TiC (
x
=0, 0.5, 1.0, 2.0 and 4.0, mass fraction, %) composites were prepared by plasma activated sintering method. The effects of TiC on the microstructure and mechanical properties of the composites were studied. The results show that with the increase of TiC content, the relative density of the composites increases first and then decreases, and the relative density of Ta-2Ti-0.5TiC reaches the highest value of 99.5%. The addition of TiC can inhibit the grain growth, and the grain size decreases with the increase of TiC content. When the TiC content is 4.0%, the grain size decreases to 2.98 µm. TiC undergoes decarburization reaction at high temperature, and the generated C reacts with Ta to generate high-hardness ceramic phase Ta
2
C in situ, which plays a role in bridging matrix grains and hindering crack propagation. The mechanical properties of Ta-2Ti-TiC composites improve with increasing TiC content, which is attributed to the benefits from grain refinement and in-situ generation of Ta
2
C high-hardness ceramic phase.
2022 Vol. 27 (6): 579-585 [
Abstract
] (
437
)
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(1076 KB) (
816
)
586
Microstructure and defects of NiCrFeAl alloy by selective laser melting
XU Ruifeng, GENG Zhaowen, CHEN Chao, ZHANG Jiaqi, LI Dan, NI Mang, ZHOU Kechao
DOI: 10.19976/j.cnki.43-1448/TF.2022033
NiCrFeAl alloy was prepared by selective laser melting (SLM) using NiCrFeAl prealloy powders as raw material. The optimizing of SLM processing parameters was carried out through optical analyzing on pores. Scanning electron microscope was ultilized for microstructure characterization of the alloy, and defects were analyzed by EBSD. The mechanical properties tests were carried out on UTM 5105 electronic universal testing machine. Results show that the optimal processing parameters of NiCrFeAl alloy fabrication are as follows: laser power of 240 W, scanning speed of 1 000 mm/s, hatching spacing of 0.12 mm and layer thickness of 0.03 mm. The corresponding tensile strength and elongation are 535 MPa and 5.8% respectively. There are solid cracks distributed between adjacent grains with large misorientation, showed intergranular fracture on horizontal and vertical cross sections. The average grain size on the horizontal cross section of the alloy is 35 μm, and the low angle grain boundaries accounts for 37.0%. The average grain size on the vertical section is 56 μm, and the low angle grain boundaries accounts for 41.0%.
2022 Vol. 27 (6): 586-594 [
Abstract
] (
536
)
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(966 KB) (
1131
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595
Hydrogen storage properties of PMMA-coated LaNi
5
alloy powders
LI Ke, GAO Yunhe, HUANG Tongwen, ZHOU Chengshang
DOI: 10.19976/j.cnki.43-1448/TF.2022045
LaNi
5
hydrogen storage alloy powders are easy to be oxidized, seriously affecting the hydrogen storage properties of LaNi
5
alloy. In this paper, PMMA (poly methyl meth acrylate) was used to modify the surface of LaNi
5
alloy by the solution impregnation method. The micrmorphology, hydrogen storage properties, and oxidation resistance of LaNi
5
alloy were investigated. The results show that the hydrogen storage capacity of air-oxidated PMMA-coated LaNi
5
alloy after oxidation is maintained at 1.29%, while that of LaNi
5
alloy decreases to 1.15% (mass fraction, %, the same below). Compared with the uncoated LaNi
5
alloy, the dehydrogenation and hydrogenation kinetic and hydrogen storage capacity of PMMA-coated LaNi
5
alloy after air-exposure are well maintained, and the PMMA-coated LaNi
5
alloy possesses good cycling stability. Therefore, PMMA-coated LaNi
5
alloy can mitigate the oxidation reaction of the alloy and improve the oxidation resistance of the alloy. It is beneficial for alloy applications and hydrogen storage safety.
2022 Vol. 27 (6): 595-600 [
Abstract
] (
587
)
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(580 KB) (
1209
)
601
Effect of boron carbide on graphitization of polyacrylonitrile based carbon fibers during spark plasma sintering
LIU Honghao, ZENG Fanhao, ZHANG Fuqin
DOI: 10.19976/j.cnki.43-1448/TF.2022053
In this paper, the C
f
/B
4
C composites were fabricated by spark plasma sintering (SPS). The graphitization degree of polyacrylonitrile (PAN) carbon fibers was characterized by X-ray diffraction and Laser Raman spectroscopy. The effects of sintering temperature, sintering pressure and holding time on the graphitization of carbon fibers were focused on. The results show that temperature, pressure and holding time have certain effects on the graphitization of carbon fibers, and the effect of temperature is the most obvious. When the sintering temperature reaches 2 000 ℃, the crystal plane spacing
d
(002) of carbon fiber by XRD and Raman peak intensity ratio (
I
D
/
I
G
) is 0.336 nm and 0.377 respectively, and the graphitization degree of carbon fibers reaches 92.21%. According to the corresponding relationship between the graphitization degree measured by XRD and Raman spectrum, the graphitization degree formula of carbon fibers characterized by Raman spectrum is fitted. The low-temperature graphitization of PAN carbon fibers under SPS is due to the fact that SPS combines the influences of temperature, pressure and current. In addition, the main catalytic mechanism is dissolution and reprecipitation. The difference of interfacial activation may be the fundamental reason for the different graphitization degree of carbon fibers.
2022 Vol. 27 (6): 601-609 [
Abstract
] (
512
)
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(0 KB)
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(642 KB) (
1420
)
610
Preparation and electrochemical properties of Ni-P-W-Mo hydrogen evolution electrode based on nickel foam
DAI Xiaomei, HE Hanwei
DOI: 10.19976/j.cnki.43-1448/TF.2022035
Nickel sulfate, sodium hypophosphite, sodium tungstate, and sodium molybdate were used as raw materials to synthesize Ni-P-W-Mo hydrogen evolution electrode on nickel foam by one-step galvanostatic electrodeposition method. The surface morphology, elemental composition, and electrochemical hydrogen evolution properties of the materials were investigated by means of X-ray diffraction, SEM, Energy X-ray spectrometry, X-ray photoelectron spectroscopy and electrochemical testing. The results show that Ni-P-W-Mo electrode has excellent catalytic activity and stability after catalyzed hydrogen evolution in alkaline solution. The current density of 10 mA/cm
2
can be reached only at 92 mV over potential, which is 67 mV lower than that of Ni-P electrode. The double-layer capacitance of Ni-P-W-Mo electrode is 42.98 mF/cm
2
. After 2000 cyclic voltammetry cycles, the hydrogen evolution activity of the electrode decreases only slightly. The excellent catalytic performance of Ni-P-W-Mo electrode may be due to the addition of W and Mo elements to the Ni-P electrode which makes the electrode surface coarser, greatly increasing the electrochemical active surface area and active site of the electrode. Meanwhile, the self-supported electrode structure can effectively reduce the interfacial transmission resistance and improve the charge transmission efficiency.
2022 Vol. 27 (6): 610-619 [
Abstract
] (
733
)
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(0 KB)
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(796 KB) (
3005
)
620
Effect of size of black phosphorene on gas sensitivity of black phosphorene/hydroxyapatite hybrid
WU Jiangsong, TANYanni, LYU Jianfeng
DOI: 10.19976/j.cnki.43-1448/TF.2022042
In this work, rod-shaped hydroxyapatite (HA) was prepared by hydrothermal method, and black phosphorene (BP) with different sizes was prepared by liquid-phase exfoliation and separated by adopting different centrifugation speed. BP/HA hybrid was prepared with BP at 7.0% mass fraction. The phase composition, micro-morphology and structure of BP/HA were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Raman spectroscopy. The gas sensing properties of pure HA and BP/HA with different sizes of BP were investigated using a gas sensing system. The results show that the addition of BP significantly improves the response of HA to ammonia, and the gas-sensing performance of HA is improved the most with the addition of BP with smaller size. Among them, the response of BP-10000/HA to the ammonia concentration of 100×10
-6
is as high as 58.7%, and when the ammonia concentration isincreased to 1 000×10
-6
, the response is as high as 98.3%. The smaller the size of BP, the better the gas sensing performance may be due to its larger specific surface area and thus more active sites. In conclusion, BP can significantly improve the gas sensitivity of HA, and BP/HA is a promising gas sensitive material at room temperature.
2022 Vol. 27 (6): 620-629 [
Abstract
] (
377
)
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(0 KB)
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(1300 KB) (
523
)
630
Crystallization behavior of self-propagating high temperature synthesis WC powder
GAO Yuyang, LIU Yong, CHEN Gang, TANG Xiaotian, ZHOU Chengshang
DOI: 10.19976/j.cnki.43-1448/TF.2022059
Single crystal WC powder was prepared by self-propagating high temperature synthesis (SHS) with wolframite (Fe(Mn)WO
4
), tungsten (WO
3
), calcium carbide (CaC
2
) and high purity aluminum powders as main raw materials. The effects of thermite addition (Fe
3
O
4
-Al mixture,
n
(Fe
3
O
4
):
n
(Al)=3:8), preheating of raw material and feeding amount on particle size and morphology characteristics of the WC powder were studied. The results show that the crystal shape of the WC powder prepared by SHS method is complete. Although the temperature of combustion system is increased with adding thermite, a large number of Fe
3
W
3
C phases are formed, resulting in a decrease in the purity of WC powder. Preheating the raw powders in the crucible can make the WC grain grow fully. The size of the WC powder becomes larger, and the WC crystal shape changes from spherical to multilateral shape. The particle size of the WC powder increases with the increase of the feeding amount of reaction material, and the shape of WC powder changes from spherical to polygonal.
2022 Vol. 27 (6): 630-637 [
Abstract
] (
487
)
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(1090 KB) (
966
)
638
Microstructure and properties of cold sprayed copper-diamond composite coatings
LIU Shuyu, PENG Yingbo, GAO Peiran, TAN Yanni, ZHANG Wei
DOI: 10.19976/j.cnki.43-1448/TF.2022057
Titanium alloys are widely used in aerospace due to their high specific strength, but the sliding friction performance is poor, which seriously affects the life of related components. Surface modification is a common method to improve the friction behavior of titanium alloy, and the metal-based diamond composite coating is one of the important research directions. In this paper, dense copper-based diamond composite coating was prepared on the surface of TC18 alloy by spray drying powder combined with cold spraying. The principle of cold spray deposition of composite powders and the correlation between microstructure and mechanical properties of coatings before and after heat treatment were explored. The results show that the composite powders prepared by spray drying meet the requirements of cold spraying process. After cold spraying, the diamond is dispersed in the coating with a mass fraction of 0.74%, and no damage or graphitization occurs. Cold sprayed diamond/copper coating shave considerable electrical conductivity and high hardness. The wear mechanism of the coatings is shear fracture and peeling. Afterheat treatment at 600 ℃, the hardness of the composite coating reduces to 95.8 HV and the conductivity increases to 89.3%IACS. The friction behavior of the coating is improved as well. The wear rate of the coating was reduced by 41%.
2022 Vol. 27 (6): 638-647 [
Abstract
] (
697
)
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(0 KB)
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(1010 KB) (
1678
)
648
Effect of load on current-carrying friction and wear performance and stability of AuNi9/PdNi-Au friction pair
YU Xinyue, MA Zhifei, ZHANG Lei, ZHANG Xin, KANG Xiao
DOI: 10.19976/j.cnki.43-1448/TF.2022068
The stability of friction and wear properties of current-carrying friction pair determines the service performance and life of the mechanism. In this paper, AuNi9/PdNi-Au friction pair with the advantages of low contact resistance and low electrical noise was selected. The current friction stability of the friction pair under 180, 280 and 380 mN loads was studied by multiple statistical evaluation indexes such as friction coefficient, contact voltage drop curve, relative stability coefficient, standard deviation and frequency distribution. The results show that when the load is 180 mN, the wear mechanism of the AuNi9 brush is mainly adhesive wear and abrasive wear. The wear mechanism of the brush is mainly fatigue wear and abrasive wear when the load increases to 380 mN. With the increase of the load, the friction stability of the AuNi9/PdNi-Au friction pair first increases and then decreases, and the electrical contact stability increases gradually. When the load is 280 mN, the average friction coefficient is 0.330, the standard deviation is 0.180, the average contact voltage drop is 89.723 mV, the standard deviation is 41.419 mV, and the brush surface roughness is 0.207 μm, all are the minimum values under three kinds of loads. The friction pair shows good current carrying friction stability.
2022 Vol. 27 (6): 648-658 [
Abstract
] (
463
)
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(0 KB)
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(1203 KB) (
1229
)
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