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2019 Vol. 24, No. 6
Published: 2019-12-15
Engineering and Technology
Engineering and Technology
491
Protonation of layered MnO
2
nanobelts and GO/MnO
2
composites and their electrochemical properties
JIA Lulu, YANG Baopeng
K
+
intercalated-MnO
2
nanomaterials were synthesized by using KMnO
4
and MnCl
2
as redox in KOH solution, placed at 200 ℃ for 48h, then protonated with ammonium persulfate. In addition, layered MnO
2
/graphene oxide (GO) composites were prepared by using graphene oxide aqueous solution as solvent. The phase and morphology of the prepared materials were characterized by XRD, SEM, etc. The electrochemical performance of the supercapacitor was tested by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) in 1 M KOH solution. The results show that the K
+
intercalated MnO
2
has the morphology of nanobelts, its length can reach 5-12 μm, and its width is about 500 nm. After protonation, high crystallinity and nanobelt morphology can be maintained. In addition, the electrochemical properties of MnO
2
can be significantly improved by the addition of GO. The specific capacitance of layered MnO
2
nanobelts/GO composites is as high as 750 F/g at current density of 0.5 A/g.
2019 Vol. 24 (6): 491-497 [
Abstract
] (
358
)
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498
Effect of heat treatment process on microstructure and mechanical properties of SLM formed Fe-35Mn Fe based high manganese alloy for automobile
LIU Lingge, ZHU Jingjin, TIAN Hailan
The selective laser melting (SLM) was used to prepare Fe-35Mn Fe-based high Mn alloy for automobile. Three heat treatment processes, namely solid solution, aging, and solid solution-aging, were used to treat the alloy, and the microstructure and mechanical properties of the alloy were analyzed and tested. The results show that Fe-35Mn alloy prepared by SLM and treated by solid solution or solution-aging treatment can refine the grain and generate many twins. Compared with the alloy of solid solution treatment, larger size grains are formed after the solid solution aging treatment, and the twins size of solution aging alloy is larger than that of solution aging alloy. After different heat treatment, Fe-35Mn alloys all produce α-Mn phase. With the increase of tensile strain, the solution alloy has the earliest plastic deformation and the best plasticity. After aging treatment, the tensile strength and yield strength of high-Mn Fe-35Mn SLM alloy increase, but the impact toughness and elongation decrease. After solution aging treatment, the number of pores is the least, the impact toughness and elongation reach the maximum (22.8 kV/J and 21.6%, respectively), and the alloy has good plasticity. Both the morphology of SLM and the tensile fracture of heat-treated Fe-35mn alloy are dimple fracture. The solution aged alloy has the least number of pores and the best plasticity.
2019 Vol. 24 (6): 498-502 [
Abstract
] (
344
)
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585
)
503
Microstructure and electrochemical properties of WO
3
-TiO
2
thin films prepared by chemical deposition on semiconductor surface
WANG Zhongli, JU Aiyun
Nano WO
3
-TiO
2
films for semiconductors were prepared by chemical deposition with different end capping agents (SDBS or PEG), and their electrochromic properties were characterized. The results show that there is a large gap between the adjacent wafers of WO
3
-TiO
2
thin film with SDBS, forming many cracks and agglomeration of particles. All the WO
3
-TiO
2
thin film samples show short wave shift in the transmission spectrum under the colored condition. There is no significant change in the transmittance of the pigmented and faded WO
3
-TiO
2
films with PEG. Better discoloration effect can be obtained when SDBS is selected as film Terminator. At the same time, the WO
3
-TiO
2
film prepared with SDBS as the terminator has a higher current density than the WO
3
-TiO
2
film prepared with PEG as the terminator. More ion implantation can be obtained, and the stability of film coloring and fading current is better.
2019 Vol. 24 (6): 503-507 [
Abstract
] (
278
)
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654
)
508
Effects of vacuum degree and carbon content on microstructure and tensile properties of M2 high speed steel
LIU Ruiqing, HE Hao, LOU Jia, LI Yimin, LI Song, LIU Chen, QIN Jianchun
The M2 high speed steel was prepared by vacuum sintering process. The effects of vacuum and carbon content on microstructure and properties of M2 high speed steel were studied. The results show that the effective sintering temperature of M2 HSS under low vacuum (10
-1
Pa) is 1 220-1 230 ℃, and its relative density is above 96%. The microstructure of M2 is composed of austenitic matrix, M
6
C and MC carbides after sintering. When vacuum degree increases to 10
-3
Pa,the effective sintering temperature of M2 HSS decreases, and the carbides in the matrix are finer and more evenly distributed. The relative density of the sintered sample is 98%, and its tensile properties and elongation reached 989 MPa and 7.1%, respectively. With the increase of carbon content, there is no obvious change in sintering interval of M2 high-speed steel, but the densification can be easier to achieve at lower temperature. When the mass fraction of carbon is 1.0%, the relative density of the sample is 97%, its tensile strength and elongation are 954 MPa and 7%, respectively.
2019 Vol. 24 (6): 508-514 [
Abstract
] (
556
)
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(1 KB)
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(1377 KB) (
708
)
515
Mechanical properties of C/TiNC coating on pole of reactive plasma spraying pumping unit
HAN Fuyong, NI Pan, HU Yangming, WANG Qin
In order to solve the problems of corrosion and wear failure of polished rod of oil field pumping unit, nano-TiCN coating was synthesized by mixing cheap graphite or carbon black powder with micro-Ti powder, feeding into high temperature plasma flame containing nitrogen, and self-propagating reaction of Ti with C and N. By adding elements such as Cr and Mo into the coating, a composite coating with micron-nano multi-scale structure is formed, which can reduce the stress of nano-TiCN coating. The results show that the hardness of C/TiCN composite coating is more than 1 500 HV, higher than that of hard Cr coating, the bonding strength of coating is more than 25 MPa, and the thickness of coating is more than 300 μm. The problem of inversion of hardness and toughness of nano-coating was solved, and the chromium plating layer on the surface of polished rod was replaced by a coating with good toughness, wear resistance and abrasion resistance, so as to prolong the service life of polished rod and disk root of oil field pumping unit and reducing the consumption of pumping unit.
2019 Vol. 24 (6): 515-522 [
Abstract
] (
343
)
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(1 KB)
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(1301 KB) (
634
)
523
Preparation and electrochemical properties of nano TiC battery anode framework materials by solid-liquid ball grinding
REN Yuduo, YAN Gang, ZHANG Shiting, LUO Kun
TiC powder was obtained by high energy ball milling of pure titanium powders and toluene. After calcination at 750 ℃ for 1h and secondary ball milling, the negative electrode of lithium-ion battery was prepared. The phase composition and microstructure of the TiC powder were analyzed and observed, the tests of the charge-discharge cycle performance of the anode material were performed. The results show that TiH
2
and WC impurities are presented in the product after ball milling, and the TiH
2
impurity is removed by vacuum calcination and secondary ball milling, higher purity TiC powder is obtained. The TiC grain size is refined and the final product grain size is 12.5 nm. The specific capacity of the TiC anode prepared by ball milling is stable during long-term discharge. When the current density is 1 A/g, the specific discharge capacity still can be maintained at 110 (mA∙h)/g when the cycle is 3 000 times. The TiC anode material has excellent long cycle performance and can be used as the framework material of Si anode material.
2019 Vol. 24 (6): 523-528 [
Abstract
] (
313
)
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(1 KB)
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(524 KB) (
672
)
529
Microstructure and mechanical properties of MoSi
2
modified C/C composites prepared by infiltration
YI Jun, ZHANG Bei, TANG Zhengxiao, XIANG Qiuling, YI Maozhong
SiC coatings were prepared on the surface and inside of porous low-density C/C composites by chemical vapor phase reaction using Si and SiO
2
powders as raw materials. MoSi
2
powder was used as raw materials to reactive infiltrate C/C composites and C/C composites with SiC interface layer to obtain MoSi
2
modified C/C composites. The microstructure of the composites was investigated by scanning electron microscopy, X-ray diffraction and electron probe microanalysis. The bending strength of the material was tested by Instron 3369 mechanical testing machine. The results show that compared with the Si-Mo modified C/C composite prepared by MoSi
2
direct infiltration, the SiC coating prepared before infiltration can effectively reduce the porosity of the SiC/C composite and obtain more compact Si-Mo modified C/C composite. The density of composites increases from 2.93 g/cm
3
to 3.20 g/cm
3
, the open porosity decreases from 10.77% to 4.07%; the flexural strength increases from 87 MPa to 121 MPa. The content of SiC and MoSi
2
in composites is higher. The composites exhibit pseudoplastic fracture behavior.
2019 Vol. 24 (6): 529-535 [
Abstract
] (
370
)
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(1 KB)
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(1461 KB) (
880
)
536
Effects of MgO-Y
2
O
3
-Re
2
O
3
on microstructure and properties of Si
3
N
4
ceramics
LU Xinxin, LIU Wei, LI Lin, LI Jianbin
Using α-Si
3
N
4
as raw powder and MgO-Y
2
O
3
-Re
2
O
3
as sintering assistant, Si
3
N
4
ceramics were prepared by hot-pressing sintering, and the density, phase composition, microstructure, thermal conductivity, bending strength and fracture toughness of Si
3
N
4
were tested by archimedean drainage method, XRD, SEM, laser flash method, three-point bending method and indentation method. Studies show that in samples with MgO-Y
2
O
3
-Re
2
O
3
(Re=Er, Sm, Dy, La, Y, Yb) added, Sm
2
O
3
, Y
2
O
3
,Yb
2
O
3
are easy to facilitate Y
2
O
3
to form the second phase Y
2
SiO
3
, Y
2
Si
3
O
3
N
4
and Y
2
SiO
5
, respectively. Meanwhile, in the Si
3
N
4
with MgO-Y
2
O
3
-Re
2
O
3
(Re=Sm, Dy, La,Yb) added, the long columnar crystals are uniformly embedded in the smaller matrix grains, with self-strengthening and toughening. The bending strength is above 920 MPa, and the fracture toughness of indentation is above 6.93 MPa∙m
1/2
. Compared with traditional binary sintering assistant MgO-Re
2
O
3
, MgO-Y
2
O
3
-Re
2
O
3
ternary additive has no regular influence on the microstructure, bending strength and fracture toughness of Si
3
N
4
ceramics with the change of Re
3+
radius, but its thermal conductivity increases with the decrease of Re
3+
radius.
2019 Vol. 24 (6): 536-541 [
Abstract
] (
342
)
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(1 KB)
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1248
)
542
Effect of B
4
C particles on microstructure and mechanical properties of C/C-SiC composites
TANG Zhenxiao, PENG Ke, XIANG Qiuling, YI Jun, YI Maozhong
B
4
C particles modified C/C-SiC composites were prepared by slurry infiltration combined with precursor infiltration and pyrolysis. The effect of the addition of B
4
C particles on the mechanical properties of C/C-SiC composites was investigated. The results show that,the flexural strength and fracture toughness of B
4
C particles modified C/C-SiC composites are 250.41 MPa and 13.56 MPa·m
1/2
, respectively. Compared with C/C-SiC composites, the flexural strength decreases by 45.5%, the toughness increases by 46.0%. The B
4
C particles can promote the sintering of SiC matrix. However, the bending strength of the composites decrease due to the formation of a large number of closed pores and weak interfaces of the matrix. The main reason for the improvement of the fracture toughness of the C/C-SiC composites modified by B
4
C particles is that the weak interface between B
4
C particles and SiC matrix make the cracks deflect effectively in the SiC matrix, increase the propagation path of the cracks in the matrix, and improve the fracture toughness of the composites.
2019 Vol. 24 (6): 542-548 [
Abstract
] (
289
)
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(1 KB)
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(775 KB) (
946
)
549
Effects of sintering temperature and heat treatment on microstructure and properties of 4605 low alloy steel prepared by powder injection molding
HUANG Yuqing, HE Hao, LOU Jia, LI Yimin, PENG Yuandong, LIU Chen, QIN Jianchun
4605 low alloy steel was prepared from 4605 master alloy powder by injection molding and sintering at 1 320-1 380 ℃. The effects of sintering temperature and heat treatment process on the microstructure, hardness and tensile strength of alloy steel were studied by three different processes of heat treatment. The results show that,the sintering density of 4605 low alloy steel increases with the increase of sintering temperature, the microstructure is composed of lath martensite and polygonal ferrite, the hardness and tensile strength of alloy steel increase with the increase of sintering temperature. The optimum properties of low alloy steel are obtained after sintered at 1 380 ℃, with its density up to 96.38% and the tensile strength is 613 MPa. The plasticity increases first and then decreases with the increase of temperature. At 1 360 ℃, the elongation of the sintered sample is optimal, reaching 13.50%. The martensite structure can be obtained through heat preservation at 800 ℃ for 0.5 h, and then at 200 ℃ for 2 h after oil quenching. The tensile strength and hardness of the sample attain to optimum, that is 708 MPa and 78.8 HRA respectively. The tempered sorbite can be obtained by heat preservation at 800 ℃ for 1 h followed by heat preservation at 600 ℃ for 2 h after oil quenching. The elongation of the sample is optimal, reaching 18.76%.
2019 Vol. 24 (6): 549-556 [
Abstract
] (
534
)
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(1 KB)
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(1291 KB) (
1666
)
557
Effect of Co-doping of MgO and Y
2
O
3
on the structure and properties of transparent alumina ceramics
LIANG Jianwei, HUANG Meipeng, LIU Wei, YANG Gao, LIAN Jiao, BO Tiezhu, XIE Zhipeng
Transparent alumina ceramic sheets were prepared by hydrogen sintering with micro-MgO, composite MgO+Y
2
O
3
(mass ratio of MgO to Y
2
O
3
is 1:1) and composite MgO+La
2
O
3
as sintering assistants. The morphology of ceramic materials was observed by scanning electron microscopy, and the transmittance was measured by spectrophotometer. The effects of the types of sintering aids and the content of MgO+Y
2
O
3
on the transmittance of transparent alumina ceramics were investigated. The results show that the addition of trace rare earth as a sintering assistants can inhibit grain growth, reduce the number of pores in the ceramic sheet, and increase the light transmittance of the alumina transparent ceramic. The transmittance the of the sample with the additive sintering assistant MgO+Y
2
O
3
is significantly higher than the sample with the single sintering assistant MgO. When the contents of the composite sintering assistants MgO+Y
2
O
3
are (0.02% to 0.05%) MgO+(0.02% to 0.05%) Y
2
O
3
(mass fraction), a transparent alumina ceramic sheet with the total light transmittance of 80% or more is obtained. However, when excessive sintering assistants are added, the light transmittance of alumina ceramics will eventually decreases due to the increase in the number of stomata.
2019 Vol. 24 (6): 557-562 [
Abstract
] (
397
)
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(1 KB)
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(510 KB) (
1318
)
563
Effect of carbon content and sintering temperature on microstructure and mechanical properties of MIM 4340 alloy steel
XU Ting, HE Hao, LOU Jia, LI Yimin, YIN Jian, LIU Chen, QIN Jianchun
4340 low alloy steel was prepared by injection molding process. The effects of carbon contents, sintering temperature and heat treatment process on microstructure and mechanical properties were studied. The results show that the powders with different carbon contents can be prepared by adding CN/OM iron powders. After sintering at 1 280-1 320 ℃ for 2 h, the sample (mass fraction of 0.50% carbon content in raw powders) is closest to the standard carbon content. The density decreases first and then increased with the increase of carbon contents, and the density increases with the increase of sintering temperature. The microstructure consists of ferrite (α-Fe), pearlite (ferrite+cementite Fe
3
C) and bainite. The tensile strength and elongation are 762.16 MPa to 1032.03 MPa and 5.25% to 8.62%, respectively. The best mechanical properties are obtained after oil quenching at 850 ℃ for 0.5 hour and tempering at 400 ℃ for 2 h. The tensile strength and elongation reaches to 1 510.24 MPa and 4.30%, respectively, and the hardness is 40.0 HRC.
2019 Vol. 24 (6): 563-570 [
Abstract
] (
455
)
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(1 KB)
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(1251 KB) (
1416
)
571
Optimized hot rolling descaling box structure before finishing rolling
ZHAO Shengli
Phosphorus removal before finish rolling (remove the oxide iron on the surface of the slab after rough rolling) is the key equipment of hot rolling line. In view of the weakness of the frame of the phosphorus removal box and the deformation of the pinch roll arch existing in the high-pressure water jet phosphorus removal, the operation of the pinch roll is not smooth and the disassembly and assembly is difficult, the main column and archway of the phosphorus removal box are grooved and corroded by high pressure water, the unreasonable design of the roller cylinder resulted in a high failure rate, and the inconsistent elevation of the phosphorus removal roller transmission mechanism. In this paper, optimizing the overall structure and layout of the dephosphorization box in finishing rolling, using the U-shaped structure and increasing the strength of the pinch roll arch to ensure the stable operation of the pinch roll, adding the protective lining plate to the parts easy to be washed out of the dephosphorization box body, optimizing the installation and connection mode of the pinch roll oil cylinder, so as to reduce the failure rate of the oil cylinder. Optimize the hydraulic lubrication system such as pinch roll, dephosphorization roll and pneumatic hydraulic device of dephosphorization tank as a whole and increase the cooling of roller table and other improvement measures, improve the overall function and performance of dephosphorization tank before finishing rolling, meet the production demand on site and improve the product quality.
2019 Vol. 24 (6): 571-576 [
Abstract
] (
390
)
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(1 KB)
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(370 KB) (
816
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