111 results on '"Laifeng Li"'
Search Results
2. Visualized Investigation of a Nitrogen Pulsating Heat Pipe
- Author
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Yaran Shi, Dong Xu, Jixiang Yan, Rendong Guo, Bingkun Lyu, Chuanjun Huang, and Laifeng Li
- Published
- 2023
3. Preliminary development of emissivity measurement system at low temperature based on radiometric method
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Yuchen Zhao, Xu Li, Hengcheng Zhang, Fuzhi Shen, Chuanjun Huang, Huiming Liu, Haoying Qi, Zichun Huang, Zhen Geng, Jijun Xin, Wei Wang, and Laifeng Li
- Subjects
General Physics and Astronomy ,General Materials Science - Published
- 2023
4. Experimental investigation of a serial-parallel configuration helium pulsating heat pipe
- Author
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Bingkun Lyu, Dong Xu, Wei Wang, Jijun Xin, Yaran Shi, Zhichun Fang, Chuanjun Huang, Rongjin Huang, and Laifeng Li
- Subjects
General Physics and Astronomy ,General Materials Science - Published
- 2023
5. Investigation on cryogenic mechanical properties of basalt fiber-reinforced epoxy composites
- Author
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Wentao Sun, Zhixiong Wu, Chuanjun Huang, Zekun Wang, Rongjin Huang, Linghui Gong, Arata Nishimura, Yuan Zhou, and Laifeng Li
- Subjects
General Physics and Astronomy ,General Materials Science - Published
- 2023
6. Mechanical properties evaluation of ReBCO CICC jacket based on super-austenitic stainless steel for CFETR high-field magnet
- Author
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Weijun Wang, Chuanyi Zhao, Huan Jin, Chuanjun Huang, Laifeng Li, Zhengping Tu, Bin Xu, Ruzong Zhai, Jiangang Li, and Jinggang Qin
- Subjects
Nuclear and High Energy Physics ,Nuclear Energy and Engineering ,Materials Science (miscellaneous) - Published
- 2023
7. Discovery of negative thermal expansion with giant thermal hysteresis in Fe3NiBx
- Author
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Kewen Shi, Rongjin Huang, Xiuliang Yuan, Jin Cui, Cong Wang, Ying Sun, and Laifeng Li
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010302 applied physics ,Diffraction ,Thermal hysteresis ,Materials science ,Condensed matter physics ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,Crystal structure ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Condensed Matter::Materials Science ,Magnetization ,chemistry ,Negative thermal expansion ,Mechanics of Materials ,0103 physical sciences ,General Materials Science ,0210 nano-technology ,Boron - Abstract
Negative thermal expansion (NTE) behavior with giant thermal hysteresis exceeding 450 K has been observed in Fe3NiBx. This behavior is desirable in the field of pipe joint or encapsulation. The temperature dependent X-ray diffraction and magnetization indicate that NTE behavior with giant thermal hysteresis is related to crystal structure transition between face-centered cubic (fcc) and body-centered cubic (bcc), but not to the magnetic transition. The introduction of boron can reduce the NTE temperature range and stabilize the high temperature fcc phase. Therefore, we can obtain the NTE behavior below room temperature during cooling process, which is important for the practical application.
- Published
- 2020
8. The Finding of Elastocaloric Effect in the Lightweight Shape Memory Mg-Sc Alloy
- Author
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Min Zhou, Rongjin Huang, and Laifeng Li
- Subjects
History ,Polymers and Plastics ,Business and International Management ,Industrial and Manufacturing Engineering - Published
- 2022
9. Physical properties of a high manganese austenitic steel Fe-30%Mn-1%C at cryogenic temperatures
- Author
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Mingyue Jiang, Chuanjun Huang, Lihe Qian, Peng Jia, Rongjin Huang, and Laifeng Li
- Subjects
General Physics and Astronomy ,General Materials Science - Published
- 2023
10. Design and construction of a 1.8 K superfluid 4He system with a G-M cryocooler
- Author
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Wei Wang, Dong Xu, Shen Fuzhi, Li Xu, Laifeng Li, Arata Nishimura, Huiming Liu, and Peng Lin
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010302 applied physics ,Materials science ,Continuous operation ,Nuclear engineering ,General Physics and Astronomy ,Cryocooler ,Cooling capacity ,01 natural sciences ,law.invention ,Superfluidity ,law ,0103 physical sciences ,Vacuum pump ,General Materials Science ,Gas cylinder ,010306 general physics ,Condenser (heat transfer) ,Superfluid helium-4 - Abstract
This paper describes a superfluid 4He (He II) production system with a G-M cryocooler developed to supply continuous cooling capacity for cryogenic devices working below 2 K, such as the sealed-cell lambda-point devices and the photon detectors. Unlike the existing cooling method that injecting and pumping liquid 4He (He I) to cool the devices, high purity 4He gas stored in gas cylinder is firstly liquefied by a G-M cryocooler in the condenser, and then cooled down under 2.17 K at the He II pot through a Joule-Thomson valve along with a dry vacuum pump. This design allows a continuous supplement of He II below 2.17 K by using 4He at ambient temperature, which avoids the temperature oscillation to the devices being cooled when refilling He I. Due to the removing of cryogen injection, no additional cryogenic apparatus and professional operation are required. In this system, the He II pot can reach a temperature below 1.8 K for continuous operation.
- Published
- 2019
11. DC surface flashover characteristics of G-11CR in vacuum from room temperature to cryogenic temperatures
- Author
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Rongjin Huang, Huiming Liu, Wei Wang, Yong Li, Chuanjun Huang, Chi Zhang, Laifeng Li, Hua Zhang, Dong Xu, Jian Li, Zhixiong Wu, Yongguang Wang, and Shibin Guo
- Subjects
010302 applied physics ,Surface (mathematics) ,Cryostat ,Materials science ,Atomic force microscopy ,General Physics and Astronomy ,Cryogenics ,01 natural sciences ,Flashover voltage ,0103 physical sciences ,Arc flash ,General Materials Science ,Composite material ,010306 general physics ,Voltage ,Weibull distribution - Abstract
A helium-free cryostat for DC flashover voltage measurement was constructed. The G-11CR film specimens were tested in vacuum at the temperatures of 293 K, 77 K and 9 K and Weibull distribution was obtained. The results show that the surface flashover voltage of G-11CR film increases as the temperature decreased. The surface flashover voltages did not decrease after 80 times successful flashover and slightly increased as the flashover time increased. Further analysis was performed to investigate the change of G-11CR surface after flashover was characterized by atomic force microscopy (AFM). G-11CR film presented different surface morphologies after 80 times successful flashover at different temperatures.
- Published
- 2019
12. Effect of filling ratio and orientation on the performance of a multiple turns helium pulsating heat pipe
- Author
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Laifeng Li, Li Monan, and Dong Xu
- Subjects
010302 applied physics ,Gravity (chemistry) ,Materials science ,General Physics and Astronomy ,chemistry.chemical_element ,Mechanics ,01 natural sciences ,Vertical orientation ,Heat pipe ,chemistry ,0103 physical sciences ,Thermal ,General Materials Science ,010306 general physics ,Adiabatic process ,Condenser (heat transfer) ,Evaporator ,Helium - Abstract
A multi-turn Pulsating Heat Pipe (PHP) made of stainless steel (I.D. 0.5 mm, O.D. 0.8 mm), filled with helium is experimentally investigated. The lengths of the evaporator, adiabatic and condenser sections are 50 mm, 100 mm and 50 mm, respectively. The study focuses on the effect of the filling ratio and the inclination angle (gravity) at different heat input levels on the thermal performance of the cryogenic PHP. Results show that the obvious temperature fluctuation occur at low filling ratios, such as 16.4%, 31.8% and 48.8%. Despite the relatively high number of turns, the gravity still plays a critical role on the PHP thermal performance, especially at medium filling ratio (i.e. 48.8%). At a filling ratio of 31.8%, 66.1% and 94.2%, the thermal performance in 60° orientation is the same as that in vertical orientation. The optimal filling ratio may be within the range between 48.8% and 66.1% and related to the heat input level.
- Published
- 2019
13. Electrical tree characteristics of epoxy resin under AC voltage at 77 K
- Author
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Zhang Hengcheng, Chuanyang Li, Rongjin Huang, Yongguang Wang, Shen Fuzhi, Hongyu Dong, Chi Zhang, Laifeng Li, Hua Zhang, and Jian Li
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010302 applied physics ,Cryostat ,Materials science ,General Physics and Astronomy ,Epoxy ,Liquid nitrogen ,01 natural sciences ,Root mean square ,Tree (data structure) ,symbols.namesake ,Tree structure ,visual_art ,0103 physical sciences ,Partial discharge ,visual_art.visual_art_medium ,symbols ,General Materials Science ,Composite material ,010306 general physics ,Raman spectroscopy - Abstract
The insulation structure which is mainly composed of epoxy resin is a key part of the superconducting magnet system. Due to the special operating environments, superconducting coils must address the challenges of cryogenic liquids and various kinds of high voltages. In this paper, the electrical tree characteristics of epoxy resin at 77 K were investigated. An experimental setup with a partial discharge (PD) device and a cryostat filled with liquid nitrogen (LN2) was set up. Optical microscopy and confocal Raman spectrometer were applied to investigate the accumulation of degradation products within the tree channels. Each group of samples was tested at a range of AC voltages (50 Hz) from 8 kV rms (root mean square) to 20 kV rms and the PD experiments were carried out at both room temperature and 77 K. The results indicated that the color of electrical trees was darker and the tree structures were more complicated at 77 K compared with those at room temperature. The weak reaction between oxygen and the degradation products within the tree channels was responsible for the darker tree channels at 77 K. The density of electrical trees increased and the damage to materials caused by electrical trees was more serious at 77 K. Meanwhile, the tree inception probability decreased and the tree growth was inhibited obviously at 77 K. It’s also revealed that the degradation products within the tree channels were confirmed to be graphitic carbon based on the corresponding Raman spectra. The size of graphitic domains within the tree channels at 77 K was more than 2 times of that at room temperature, which contributed to the tree growth acceleration in the later growth stage at 77 K.
- Published
- 2019
14. Adjustable thermal expansion in La(Fe, Si)13-based conductive composites by high-pressure synthesis
- Author
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Wei Wang, Laifeng Li, Yuqiang Zhao, Shibin Guo, Xinran Shan, Chuanjun Huang, Yi Shan, and Rongjin Huang
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Materials science ,business.industry ,02 engineering and technology ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Physical property ,Thermal conductivity ,Semiconductor ,Negative thermal expansion ,Phase (matter) ,lcsh:TA401-492 ,Microelectronics ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,Composite material ,0210 nano-technology ,business - Abstract
Providing a suitable contact interface, where a high conductivity material with a desirable coefficient of thermal expansion (CTE) adjoins the target micro-electric devices, is very crucial to optimize the properties and service life of the relevant instruments. Regrettably, a high conductivity, low thermal expansion and relatively inexpensive material is very rare. Composites, fortunately, can offer a method to design materials with adjustable properties by mixing two or more diverse constituents. In this paper, high conductivity composites with adjustable thermal expansion were successfully prepared by a high-pressure synthesis. The composites are based on combining La(Fe,Si)13-based compounds, the materials showing a giant, isotropic negative thermal expansion (NTE) properties, within Cu matrix. The La(Fe,Si)13-based compounds were used to adjust the CTE of the composites, while the Cu phase is in charge of tuning the thermal conductivity properties. Thus, by changing the relative amount of the two components, the composites with high conductivities and adjustable CTE were achieved. Furthermore, the thermal expansion and magnetic properties of the composites were investigated by a physical property measurement system. The present results highlight the potential applications of the Cu-based high conductivity composites with room-temperature NTE properties in the thermal contacts to various semiconductor and microelectronic devices. Keywords: La(Fe, Si)13-based compounds, Metal-matrix composites, Negative thermal expansion
- Published
- 2019
15. Development of welding and processing technologies of helium inlet for ITER Correction Coil
- Author
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Jing Wei, Laifeng Li, Chao Fang, Jijun Xin, Lin Wang, Yuntao Song, Chuanjun Huang, and Shuangsong Du
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Superconductivity ,Leak ,Materials science ,Mechanical Engineering ,Nuclear engineering ,Nozzle ,chemistry.chemical_element ,Welding ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Conductor ,Nuclear Energy and Engineering ,chemistry ,Electromagnetic coil ,law ,0103 physical sciences ,General Materials Science ,010306 general physics ,Electrical conductor ,Helium ,Civil and Structural Engineering - Abstract
The ITER Correction Coil (CC) was wound with cable-in-conduit conductors (CICC) in a square 316 L stainless steel jacket into multiple pancakes embedded into the coil case. These coils relied on the CICC, the supercritical cooling circuit of which contained helium inlets and outlets. The oblong weld used to connect the nozzle to the stainless steel conductor is a critical process and required full penetration through the thickness of the nozzle. The special welding clamp contained a cooling block was designed to control the total deformation of the nozzle and the temperature of the superconducting strands. The data concerning the temperature gathering of the superconducting strand shows that the maximum temperature was lower than the allowed temperature, and thus did not degrade the superconducting strand. Based on the metallographic examination, some defects in the weld were found and corrected to meet the requisite requirements following the backing clean-up process. Volumetric X-Ray examination revealed no defects after the clean-up process, and fatigue and leak tests proved the reliability of nozzle weld as well as its welding and processing.
- Published
- 2018
16. Effect of number of turns and configurations on the heat transfer performance of helium cryogenic pulsating heat pipe
- Author
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Li Monan, Laifeng Li, and Dong Xu
- Subjects
Materials science ,020209 energy ,General Physics and Astronomy ,02 engineering and technology ,Mechanics ,Cryocooler ,Cooling capacity ,01 natural sciences ,Heat pipe ,Thermal conductivity ,0103 physical sciences ,Heat transfer ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,010306 general physics ,Adiabatic process ,Condenser (heat transfer) ,Evaporator - Abstract
The pulsating heat pipe (PHP) is a potential alternative to highly conductive metals such as copper for long distance heat transfer. Effective thermal conductivity and heat transfer capacity of a PHP are two of the most critical factors for practical applications. In this paper, a helium based PHP, which consists of 48 parallel tubing sections, was developed. The lengths of the evaporator, adiabatic and condenser sections are 50 mm, 100 mm and 50 mm respectively. The condenser section was thermally anchored to a Gifford-McMahon cryocooler (GM cryocooler) with a cooling capacity of 1.5 W at 4.2 K. A maximum effective thermal conductivity of 12330 W/m∙K was obtained when 1.1 W heat was applied to the evaporator section at a fill ratio of 70.5%. With the same geometric parameters and operational parameters, the effect of the number of turns on the heat transfer performance was figured out by comparing the 48-turn PHP with an 8-turn PHP. The results show that the temperature difference between the evaporator and condenser sections of the 48-turn PHP is much smaller than that of the 8-turn PHP. The dry-out temperature response, effective thermal conductivity and heat transfer capacity of them are obtained and analyzed. Furthermore, two configurations of the 48-turn PHP, a parallel configuration and a series configuration, are defined. An optimum configuration is proposed and makes a reference to the design of a cryogenic PHP for applications.
- Published
- 2018
17. Correlation between microstructure evolution and cryogenic fracture toughness in aging ITER-grade 316LN weldments
- Author
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Jijun Xin, Chuanjun Huang, Jing Wei, Laifeng Li, Yuntao Song, and Chao Fang
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Toughness ,Materials science ,Gas tungsten arc welding ,technology, industry, and agriculture ,General Physics and Astronomy ,02 engineering and technology ,Welding ,respiratory system ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Fracture toughness ,law ,0103 physical sciences ,Ultimate tensile strength ,Fracture (geology) ,General Materials Science ,Composite material ,0210 nano-technology ,Joint (geology) - Abstract
In the present work, the correlation between microstructural evolution and fracture toughness in 316LN joints welded by Tungsten Inert Gas (TIG) was investigated. The effect of post-weld heat treatment (PWHT) on the microstructure and toughness was characterized. The welding process can significantly change the equiaxed grains of base metal to cells and dendrites, while the PWHT can increase the dendrite size, mitigate the texutre intensity, reduce the dislocation density, and slightly weaken the ultimate tensile strength of the joints. Fracture toughness tests reveal that the strain-induced martensitic transformation at cryogenic temperatures can remarkably deteriorate the fracture toughness. Due to the microstructural evolution during PWHT, the J-integral values at 77 K and 4.2 K decrese to 85% and 54% of those in the as-welded conditions, respectively. The fracture morphology of the as-welded joint shows a characterization of ductile fracture, while the PWHT joint features a mixture of ductile and brittle fracture.
- Published
- 2018
18. Enhanced Superelasticity and Reversible Elastocaloric Effect in Nano-NiTi Alloys with Low Stress Hysteresis
- Author
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Min Zhou, Wei Wang, Fangzheng Guo, Haojian Su, Rongjin Huang, Xiao Yang, and Laifeng Li
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History ,Polymers and Plastics ,Business and International Management ,Industrial and Manufacturing Engineering - Published
- 2021
19. Effect of Co on phase stability and mechanical behavior of CoxCrFeNiMnAl0.3 high entropy alloys with micro/nano hierarchical structure
- Author
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Guannan Zhang, Xiao Yang, Wu Qi, Yong Li, Wei Wang, Yixiang Chen, Jiangtao Li, and Laifeng Li
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High-entropy alloys ,Mechanics of Materials ,Phase stability ,Micro/nano hierarchical structure ,Mechanical Engineering ,TA401-492 ,CoxCrFeNiMnAl0.3 ,General Materials Science ,Mechanical behavior ,Materials of engineering and construction. Mechanics of materials - Abstract
Co-Cr-Fe-Ni-Mn high entropy alloys (HEAs) have attracted extensive attention due to their broad cryogenic engineering application potential, reasonable control of alloying elements can significantly improve its mechanical performance. In this work, the effects of Co content on the phase stability and mechanical behavior CoxCrFeNiMnAl0.3 HEAs were investigated. It is found that with the decrease of the Co content, the stability of the face-centered cubic (FCC) solid solution phase in the alloy decreases, resulting in the precipitation of the BCC (body-centered cubic) phase from the FCC phase, thereby obtaining the FCC + BCC dual-phase structure. During annealing, the precipitated BCC phase can effectively suppress the grain growth and recrystallization of the FCC solid solution, forming an ultrafine-grained microstructure. In addition, the Ni-Al type nano-B2 phase can form in the BCC phase under the influence of the negative formation enthalpy during solidification. This micro/nano hierarchical structure can effectively improve the mechanical properties of the alloys. Co0.25CrFeNiMnAl0.3 maintains relatively excellent tensile yield strength (486 MPa), the tensile elongation remains above 20 %. This study regulates the formation of the BCC phase and B2 phase by reducing the content of Co, which provides a new idea for the preparation of low-cost HEAs with excellent mechanical properties.
- Published
- 2022
20. Liquid helium temperature deformation and local atomic structure of CoNiV medium entropy alloy
- Author
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Raymond Kwesi Nutor, Tianding Xu, Xuelin Wang, Xiao-Dong Wang, Pengfei An, Jing Zhang, Tiandou Hu, Laifeng Li, Qingping Cao, Shaoqing Ding, Dongxian Zhang, and Jian-Zhong Jiang
- Subjects
Mechanics of Materials ,Materials Chemistry ,General Materials Science - Published
- 2022
21. Hyperbranched graphene oxide structure-based epoxy nanocomposite with simultaneous enhanced mechanical properties, thermal conductivity, and superior electrical insulation
- Author
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Zhicong Miao, Shiyong Xie, Laifeng Li, Zhixiong Wu, Rongjin Huang, Zhengrong Zhou, Yalin Zhao, and Shibin Guo
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chemistry.chemical_classification ,Nanocomposite ,Materials science ,Graphene ,General Engineering ,Oxide ,Izod impact strength test ,Epoxy ,Polymer ,law.invention ,chemistry.chemical_compound ,Compressive strength ,chemistry ,law ,visual_art ,Ultimate tensile strength ,Ceramics and Composites ,visual_art.visual_art_medium ,Composite material - Abstract
The combination of graphene oxide (GO) nanosheets and polymer matrix provides an opportunity to synthesize polymer composites with excellent engineering application performance. However, the preparation of high-performance GO-based composites is difficult because the nano-scaled GO is easily agglomerated, and the weak interface bonding force between the GO and polymer. Herein, a simple and effective method for preparing GO-based composites via hyperbranched polymer (HPB) grafting is presented. The resulting HPB-GO has uniformly dispersed in the epoxy resin (EP) matrix and combines with the matrix through chemical bonds, which has a strong interfacial acting force and improves the load transfer efficiency of the matrix to HPB-GO. Thus, the resultant EP/HPB-GO nanocomposite exhibited superior mechanical properties with a dramatic increase with only 0.2 wt% HPB-GO loading, the impact strength, the tensile strength, and the compression strength, i.e., 58.53%, 83.29%, and 57%, respectively, when compared to pure epoxy resin. Meanwhile, the nanocomposite exhibits an 80% increase in thermal conductivity (0.32 W m−1 K−1). Moreover, outstanding electrical insulation performance is obtained. The ultra-low content of HPB-GO significantly improves the performance of epoxy resin, which provides an economical and effective method to broaden the application of epoxy resin in engineering.
- Published
- 2022
22. Ne-liquefaction system development for the 940 nm infrared optical characteristics measurement
- Author
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Hengcheng Zhang, Wei Xie, Shuai Meng, Shanshan Wu, Xiaojun Wang, Zhongzheng Chen, Chuanjun Huang, Rongjin Huang, and Laifeng Li
- Subjects
General Physics and Astronomy ,General Materials Science - Published
- 2022
23. Mechanical properties and microstructure evolution of cryogenic pre-strained 316LN stainless steel
- Author
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Wei Wang, Yuan Zhou, Zhengrong Zhou, Zhang Hengcheng, Laifeng Li, Wu Shanshan, Jijun Xin, Chuanjun Huang, and Wei Xie
- Subjects
Materials science ,Diffusionless transformation ,Phase (matter) ,Martensite ,Ultimate tensile strength ,General Physics and Astronomy ,General Materials Science ,Elongation ,Dislocation ,Composite material ,Microstructure ,Indentation hardness - Abstract
The 316LN stainless steel (SS) used for TF conduits in the ITER must undergo a series of pre-deformation during the fabrication. In order to investigate the variation of mechanical properties of 316LN SS with different temperature and cryogenic pre-strain, the cryogenic pre-strained samples with 0%, 15%, 25%, and 35% pre-strain were prepared and stretched at room temperature (RT), 77 K and 4.2 K, respectively. The yield strength (YS), ultimate tensile strength (UTS), elongation and microhardness of the samples were measured. Besides, the Scanning Electronic Microscopy (SEM) and Transmission Electronic Microscopy (TEM) were applied to observe the microstructure of 316LN SS. The magnetic measurements for the samples were carried out to investigate the volume percent of phase transformation. The results indicate that the YS, UTS and microhardness of 316LN SS are improved by means of cryogenic pre-strain and the decrease of elongation of pre-strained samples is different at different temperatures. All 316LN samples show the ductile fracture. The dislocation of samples promotes by cryogenic pre-strain and hinders by cryogenic temperatures. The martensitic transformation occurs after all pre-strained samples were stretched. The volume percent of α’ martensite is minimal at RT and increases dramatically at cryogenic temperatures (77 K and 4.2 K). The combination of dislocation density and martensitic transformation results in changes in the 316LN SS mechanical properties.
- Published
- 2022
24. Weathering dynamics reflected by the response of riverine uranium isotope disequilibrium to changes in denudation rate
- Author
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Jun Chen, Tao Li, Laura F. Robinson, Tianyu Chen, A. Joshua West, Chen-Feng You, Gaojun Li, Yang Chen, Gen Li, Liang Zhao, Weihua Wu, Le Li, Laifeng Li, and David W. Hedding
- Subjects
landscape evolution ,010504 meteorology & atmospheric sciences ,chemistry.chemical_element ,Soil science ,Weathering ,010502 geochemistry & geophysics ,01 natural sciences ,soil ,Geochemistry and Petrology ,TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY ,carbon cycle ,Earth and Planetary Sciences (miscellaneous) ,Dissolution ,0105 earth and related environmental sciences ,critical zone ,Isotopes of uranium ,Secular equilibrium ,Uranium ,erosion ,Regolith ,Geophysics ,Denudation ,chemistry ,Space and Planetary Science ,Erosion ,Geology - Abstract
The ratio between the activity of dissolved 234U and 238U in river water, (234U/238U)Riv, shows promise for tracing weathering processes. It has been suggested that preferential 234U release generates a high (234U/238U)Riv under low weathering intensity while congruent weathering, as expected for high weathering intensity, would release uranium with a secular equilibrium (234U/238U)Riv of 1. However, weathering intensity depends on the combination of exposure age of weathering interfaces and dissolution rate, complicating the use of (234U/238U)Riv as a tool in weathering studies. This work attempts to resolve the weathering dynamics reflected by (234U/238U)Riv using catchment scale denudation rate (D) as a first order approximation for the age of weathering interfaces. A global dataset (n=653), including 132 new measurements from Chinese catchments, indicates changing responses of (234U/238U)Riv to D. Higher values (>1.5) and larger variability of (234U/238U)Riv are observed in catchments both with high (>3 mm/yr) and low D (234U/238U)Riv are associated with catchments of medium to high D (0.3–2 mm/yr). The observed pattern can be explained by a model that involves competing uranium release from active- and inactive-weathering interfaces in response to a shifting weathering regime, from kinetically-limited to supply-limited. (234U/238U)Riv decreases with decreasing D under a kinetically-limited weathering regime due to the increasing contribution of congruent weathering relative to the preferential dissolution of 234U from radioactively damaged sites as D decreases. In contrast, (234U/238U)Riv increases with decreasing D under a supply-limited weathering regime because the minerals that remain under these conditions continue to release 234U to solution by recoil, while contributing little to the dissolved 238U because of their slow dissolution rate. A much deeper depth of the weathering interface is suggested for catchments with high D due to higher weathering contribution from deep fractures relative to the poorly developed surface regolith. A young age of ∼10 kyrs is constrained by the model for complete dissolution of exposed weathering-active minerals, which implies a rapid shifting from kinetically-limited to supply-limited weathering regime and limited influence of weathering on the calculation of comminution age based on (234U/238U) in sediments. A site-specific dissolution rate that is consistent with those estimated from weathering profiles is also constrained, which suggests that the discrepancy between field and laboratory weathering rate may largely be controlled by the difference in chemical affinity associated with stagnant micro-pores, low permeability, and high rock/fluid ratios rather than the passivation of weathering interfaces.
- Published
- 2018
25. Adjustable zero thermal expansion in Ti alloys at cryogenic temperature
- Author
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Laifeng Li, W. H. Wang, X.Q. Zhao, Xixian Yang, Yiyin Shan, Hui Jun Liu, Chuangjun Huang, Ruilin Huang, and Yuqiang Zhao
- Subjects
Materials science ,Cryogenic engineering ,Mechanical Engineering ,Alloy ,Metals and Alloys ,Zero (complex analysis) ,Titanium alloy ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Condensed Matter::Materials Science ,Mechanics of Materials ,Thermal ,Materials Chemistry ,engineering ,Composite material ,0210 nano-technology ,Cryogenic temperature - Abstract
Titanium alloys are widely used in cryogenic engineering due to their excellent mechanical properties. In this paper, through optimizing the alloying elements and proper thermomechanical treatments, an adjustable zero thermal expansion in Ti alloy is obtained. The achieved materials show a very low coefficient of linear thermal expansion in a wide temperature region (100–623 K). Our study indicated that the thermal expansion property of the Ti alloys can be tuned by cold rolling and the thermal history. This unique alloy may potentially be developed to prepare the important parts for cryogenic practical applications as a controllable zero thermal expansion material.
- Published
- 2018
26. Tunable near-zero thermal expansion in the C-doped La(Fe, Si)13 compounds at cryogenic temperatures
- Author
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Shibin Guo, Wei Wang, Chuanjun Huang, Laifeng Li, Yi Shan, Hailin Dai, Rongjin Huang, and Yuqiang Zhao
- Subjects
Materials science ,Condensed matter physics ,Mechanical Engineering ,Doping ,Zero (complex analysis) ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Magnetic exchange ,Mechanics of Materials ,General Materials Science ,0210 nano-technology ,Magnetic analysis - Abstract
The controllable thermal expansion property gives us a method to design materials with desirable coefficient of thermal expansion. In this paper, we report a tunable zero thermal expansion (ZTE) in C-doped La(Fe, Si)13 compounds over a wide operation-temperature window (77–260 K). The effects of the interstitial C atoms on the thermal expansion and magnetic properties of the LaFe10.0Si3.0Cx (x = 0, 0.2, 0.3, 0.4) compounds were respectively investigated. The further magnetic analysis indicates that the ZTE behaviors of this La(Fe, Si)13-based compounds are attributed to the changes of magnetic exchange couplings because of the introduction of interstitial C atoms.
- Published
- 2019
27. Electrical performance of TGPAP and DGEBF-based epoxy resin insulation materials for superconducting magnets
- Author
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Shuo Xu, Shaohe Wang, Laifeng Li, Sichen Qin, Zhixiong Wu, and Youping Tu
- Subjects
010302 applied physics ,Permittivity ,Materials science ,Diglycidyl ether ,Dielectric strength ,Mechanical Engineering ,Glass fiber ,Dielectric ,Epoxy ,01 natural sciences ,chemistry.chemical_compound ,Nuclear Energy and Engineering ,chemistry ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,General Materials Science ,Dielectric loss ,Composite material ,010306 general physics ,Curing (chemistry) ,Civil and Structural Engineering - Abstract
For the insulation materials of the superconducting magnet, the mechanical and electrical properties should be guaranteed under stresses of cryogenic temperature and intense radiation. In this study, two types of epoxy resins were prepared, which consist of diglycidyl ether of bisphenol-F (DGEBF) and triglycidyl-p-aminophenol (TGPAP) as matrixes respectively, and diethyl toluene diamine (DETD), isopropylidenebisphenol bis[(2-glycidyloxy-3-n-butoxy)-1-propylether] (IPBE) and boron-free glass fibre were used as curing, toughing and reinforcing agents for each resin. The direct-current (dc) electric breakdown strength and flashover voltage, dielectric properties and space charge characteristics of both epoxy composites were investigated. According to the results, DGEBF composite shown a higher dielectric strength, lower permittivity and dielectric loss at cryogenic temperature and smaller shallow trap density, which makes it more potential to be used for the cryogenic insulation.
- Published
- 2017
28. The microstructures and mechanical properties of dissimilar laser welding of copper and 316L stainless steel with Ni interlayer
- Author
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Chuanjun Huang, Zhichun Fang, Dong Wu, Shanlin Wang, Jing Wei, Laifeng Li, Wei Wang, Jijun Xin, Wenjun Sun, and Zhang Hengcheng
- Subjects
Materials science ,General Physics and Astronomy ,chemistry.chemical_element ,Laser beam welding ,Welding ,Microstructure ,Copper ,law.invention ,chemistry ,law ,Dimple ,Ultimate tensile strength ,Fracture (geology) ,General Materials Science ,Composite material ,Joint (geology) - Abstract
To improve the quality of welded joints between copper and 316L stainless steel, laser welding with Ni interlayer was carried out. A sound welded joint was obtained and the microstructures as well as mechanical properties were investigated. Results indicate that no welding defects or spherical particles were formed in the fusion zone. The microstructures in the fusion zone were characterized as dendritic grains, and no macroscopic segregation was observed. The welded joint failed at copper base material with an average tensile strength of 408 MPa at 77 K, and ductile fracture mode with dimples on the fracture surface were presented. Moreover, the addition of Ni interlayer prevents formation of welding defects and spherical particles and improves mechanical properties of the joint.
- Published
- 2021
29. 2 K Cryogenic system with the thermal switch for measuring electrical properties of insulation materials
- Author
-
Rongjin Huang, Dong Xu, Yuchen Zhao, Huiming Liu, Jia Peng, Laifeng Li, Haoying Qi, Arata Nishimura, and Zhang Hengcheng
- Subjects
Cryostat ,Materials science ,Nuclear engineering ,General Physics and Astronomy ,chemistry.chemical_element ,High voltage ,Flange ,Cryocooler ,chemistry ,Arc flash ,General Materials Science ,Superfluid helium-4 ,Helium ,Voltage - Abstract
A cryogenic system has been established to measure electrical properties of insulation materials. The cryostat in the system contains two operating modes: 4.2 K and 1.65 K. A G-M cryocooler is used as cold source in these two modes. In 4.2 K mode, samples were directly cooled by the copper plates connected to the second stage of the cryocooler. In the 1.65 K mode, the helium gas is liquefied. The superfluid 4He (He-Ⅱ) of 1.65 K was obtained by throttling and depressurizing the liquid 4He (He-Ⅰ). The thermal switch in the 1.65 K mode can reduce the precooling time by 11.6 h and saved 22.5 L of helium. The transforming of the two modes is controlled by four threaded rods which are connected to the first and the second stage flange. The electrical test unit is designed, including the breakdown strength test and the flashover characteristics test with the voltage from 0 to 100 kV, which realizes the coupling of low temperature and high voltage.
- Published
- 2021
30. A 20 K cryogen-free leak detection system for cryogenic valves by using a GM cryocooler
- Author
-
Zhang Hengcheng, Laifeng Li, Lyu Bingkun, Rongjin Huang, Huiming Liu, Tao Wang, Arata Nishimura, Chuanjun Huang, and Dong Xu
- Subjects
Materials science ,Cryogenic engineering ,Physics::Instrumentation and Detectors ,Nuclear engineering ,Water cooling ,General Physics and Astronomy ,General Materials Science ,Solenoid ,Helium mass spectrometer ,Liquid oxygen ,Cryocooler ,Liquid hydrogen ,Leakage (electronics) - Abstract
Sealing performance under cryogenic temperatures should be a consideration in the development of a cryogenic valve for use in cryogenic engineering. In the present work, a cryogen-free leak detection system at 20 K to conduct leakage testing of cryogenic valves was developed. The experimental system was composed of a cooling system, a leak detection system, and a PLC (Programmable Logic Controller) system. Compared with the traditional cryogenic leak detection systems, this system using the GM cryocooler instead of cryogen is beneficial for the application for its low operating cost, simple structure, and safe handling. Five valves can be installed simultaneously and tested in sequence. The helium mass spectrometer leak detector is used for its sensitive response and high precision. The reliability of this system was verified by testing the leak rate of the system itself. Three high-pressure cryogenic solenoid valves were tested using helium gas under the pressure varied from approximately 2.5 bar to 80 bar and at both room temperature (300 K) and liquid hydrogen temperature (20 K). The tested valves can be cooled from room temperature to 18 K within 6 h. The test results of the internal leakage rate and the external leakage rate of the samples were discussed. This system will aid in the inspection of many critical cryogenic components such as liquid oxygen and liquid hydrogen valve assemblies for which leakage may lead to serious consequences.
- Published
- 2021
31. Qualification of structural stainless steel products for the ITER correction coil cases
- Author
-
Jing Wei, Laifeng Li, Ignacio Aviles Santillana, Paul Libeyre, S. A. E. Langeslag, F. Simon, Zhiyong Chai, Stefano Sgobba, and Jean-Michel Dalin
- Subjects
Toughness ,Fabrication ,Materials science ,business.industry ,Mechanical Engineering ,Weldability ,Mechanical engineering ,01 natural sciences ,Steelmaking ,Forging ,010305 fluids & plasmas ,Conductor ,Nuclear Energy and Engineering ,Electromagnetic coil ,0103 physical sciences ,Homogeneity (physics) ,General Materials Science ,010306 general physics ,business ,Civil and Structural Engineering - Abstract
The ITER Correction Coils (CCs) consist of three sets of six coils, Bottom (BCC), Side (SCC) and Top Correction Coils (TCC), respectively. The CCs rely on 10 kA NbTi cable-in-conduit conductor. Each CC winding pack is enclosed inside a 20 mm thick 316LN stainless steel case, providing structural reinforcement against the electromagnetic loads arising in the winding pack. The material of coil cases shall feature ready weldability both by laser and conventional techniques, high strength and toughness at 4 K. Material production involves not only hot rolled plates of different thicknesses, but also heavy gauge extrusions. An adapted steelmaking route including Electroslag Remelting (ESR) combined with a hot transformation step involving redundant multidirectional forging of the slabs and of the billets was adopted. This route allowed the stringent material specification to be fulfilled and permitted to achieve cleanliness, fineness of the structure and homogeneity on the final products. An extensive follow-up of the steel manufacturing through systematic non-destructive and destructive examinations was carried out in order to ascertain the soundness and the homogeneity of the final products. The progresses accomplished throughout the steel manufacturing are highlighted. The properties achieved on the final products that were enabled by the selected manufacturing route are discussed.
- Published
- 2017
32. Liquid helium free mechanical property test system with G-M cryocoolers
- Author
-
Yemao Han, Chuanjun Huang, Rongjin Huang, Huiming Liu, Laifeng Li, Dong Xu, and Zhang Hengcheng
- Subjects
010302 applied physics ,Work (thermodynamics) ,Universal testing machine ,Materials science ,Tension (physics) ,Liquid helium ,Nuclear engineering ,General Physics and Astronomy ,Fracture mechanics ,Cryocooler ,01 natural sciences ,law.invention ,law ,0103 physical sciences ,Ultimate tensile strength ,Heat transfer ,General Materials Science ,010306 general physics - Abstract
In the present work, a cryogenic mechanical property testing system conduction-cooled by two G-M cryocoolers was developed. The testing sample can be cooled from room temperature to 2.7 K within 7.5 h. The sample was first cooled down to 11.1 K directly by the two G-M cryocoolers and then cooled down to 2.7 K by decompressing the chamber. Instead of liquid helium, the cooling process is characterized by cooling with recycled helium gas as heat transfer medium. The heat load of the system was analyzed and optimizations were adopted in terms of material selections and design. The static load capacity of the system reaches 200 kN and the fatigue load capacity can reach 50 kN. This system can be installed onto an electronic universal testing machine or a fatigue testing machine to characterize static tension, fracture mechanics or fatigue properties at tunable low temperatures. Tensile properties of 316L austenitic stainless steels at 4.2 K were tested with the system and the results were compared with those obtained by cooled using liquid helium, which demonstrates high reliability.
- Published
- 2017
33. Uranium comminution age tested by the eolian deposits on the Chinese Loess Plateau
- Author
-
Junfeng Ji, Jun Chen, Tao Li, Xiangjun Liu, Liang Zhao, Laifeng Li, Gaojun Li, and Le Li
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Isotopes of uranium ,Bedrock ,chemistry.chemical_element ,Mineralogy ,Weathering ,Uranium ,010502 geochemistry & geophysics ,01 natural sciences ,Geophysics ,chemistry ,Space and Planetary Science ,Geochemistry and Petrology ,Dust storm ,Earth and Planetary Sciences (miscellaneous) ,Aeolian processes ,Comminution ,Dissolution ,Geology ,0105 earth and related environmental sciences - Abstract
The U 234 /238U ratio of fine particles can record the time since their separation from bed rock because of the disruption of uranium series equilibrium introduced by the recoil of daughter 234Th nuclei (precursor of 234U) out of particle surfaces during the decay of 238U. Application of the uranium comminution age method, which has great potential in tracing production and transportation of sediments is however complicated by the weathering dissolution of U 234 depleted particle surfaces, the difficulty in determining the fraction of recoiled nuclei, and the precipitation of exogenetic U 234 . Here we minimize these complications by using a newly developed precise size separation using electroformed sieve, and a chemical protocol that involves reductive and oxidative leaching. Eolian deposits collected from the Chinese Loess Plateau (CLP) were used to test the validity of our method. Possible effects of weathering dissolution were also evaluated by comparing samples with different weathering intensities. The results show decreasing 234U/238U ratios in fine eolian particles with increasing sedimentation age, agreeing well with the theoretical prediction of the comminution age model. This successful application of the uranium comminution age approach to the eolian deposits on the CLP is also aided by a stable dust source, the low weathering intensity, the lack of consolidation, and the well-defined age model of the deposits. A transportation time of 242 ± 18 ka was calculated for the eolian deposits, which indicates a long residence time, and thus extensive mixing, of the dust particles in source regions, partly explaining the stable and homogeneous composition of the eolian dust over glacial–interglacial cycles.
- Published
- 2017
34. Effect of secondary phases on thermoelectric properties of Cu 2 SnSe 3
- Author
-
Guanghua Liu, Min Zhou, Laifeng Li, Rui Ma, Jiangtao Li, Yemao Han, Yuyang Li, and Kexin Chen
- Subjects
Secondary phase ,Materials science ,Process Chemistry and Technology ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,Thermoelectric effect ,Materials Chemistry ,Ceramics and Composites ,0210 nano-technology ,Monoclinic crystal system - Abstract
Cu 2 SnSe 3 samples with different secondary phases are prepared from compositions of Cu x SnSe 3 (x=1.8–2.2) and Cu 2 Sn y Se 3 (y=0.8–1.2), and their thermoelectric properties are investigated. For Cu x SnSe 3 samples, the secondary phase is SnSe 2 for x=1.8 and 1.9 and SnSe for x=2.2, and nearly single-phase Cu 2 SnSe 3 is obtained for x=2.0 and 2.1. For Cu 2 Sn y Se 3 samples, the secondary phase is CuSe for y=0.8 and SnSe for x=1.1 and 1.2, and single-phase Cu 2 SnSe 3 is produced for y=0.9 and 1.0. The lattice structure of synthesized Cu 2 SnSe 3 depends on the x and y values, which is cubic for x≤2.0 or y≤1.0 and monoclinic for x>2.0 or y>1.0. Compared with the single-phase Cu 2 SnSe 3 sample (ZT=0.4 2 at 77 3 K), the samples with SnSe 2 secondary phase show a greatly-enhanced ZT of 0.84 at 773 K, which is likely the best result for un-doped Cu 2 SnSe 3 up to now. The samples with SnSe secondary phase exhibit poor thermoelectric properties.
- Published
- 2017
35. Growth of FeSe 0.5 Te 0.5 crystals with (001) preferred orientation by chemical-furnace-assisted combustion synthesis
- Author
-
Wei Wang, Guanghua Liu, Laifeng Li, Kexin Chen, and Jiangtao Li
- Subjects
Materials science ,Crystal growth ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Combustion ,01 natural sciences ,Chemical reaction ,Crystal ,Crystallinity ,Tetragonal crystal system ,Iron-based superconductor ,Crystallography ,Chemical engineering ,0103 physical sciences ,Volume fraction ,General Materials Science ,010306 general physics ,0210 nano-technology - Abstract
Iron-based superconductor of FeSe0.5Te0.5 has been prepared by chemical-furnace-assisted combustion synthesis. The chemical furnace preheats the reactant and enhances the reaction temperature, thus increasing the volume fraction of liquid and the solubility of Fe and improving the mass transfer. Accordingly, the chemical reaction and crystal growth are greatly promoted, resulting in higher compositional homogeneity, better crystallinity, and larger crystal size. The synthesized FeSe0.5Te0.5 sample consists of two-dimensional thin slice crystals. It is proposed that, the slice crystal shape is derived from the intrinsic tetragonal lattice of FeSe0.5Te0.5, and forms by anisotropic crystal growth with fast growth in (001) face. The crystal growth of FeSe0.5Te0.5 is also affected by cooling condition, and by control of the cooling condition lamellar crystals are produced with a thickness of about 1 mm and (001) preferred orientation. The transport properties of the synthesized FeSe0.5Te0.5 sample have been investigated, showing an onset Tc of about 13 K in the resistivity vs. temperature curve and a sharp drop of magnetic susceptibility at about 15 K. Compared with the conventional solid state reaction approach, chemical-furnace-assisted combustion synthesis may provide a more efficient way to prepare iron-based superconductors with much-reduced processing time and not requiring furnaces.
- Published
- 2017
36. Continued obliquity pacing of East Asian summer precipitation after the mid-Pleistocene transition
- Author
-
Wenfang Zhang, Zeke Zhang, Chen-Feng You, Junfeng Ji, Fei Liu, Hou Chun Liu, Jun Chen, Tao Li, Liang Zhao, Laifeng Li, Gaojun Li, Hemmo A. Abels, Renyuan Xia, Chao Ren, and Le Li
- Subjects
geography ,Milankovitch cycles ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Pleistocene ,Speleothem ,Climate change ,010502 geochemistry & geophysics ,Monsoon ,01 natural sciences ,Geophysics ,Boreal ,Space and Planetary Science ,Geochemistry and Petrology ,Climatology ,Earth and Planetary Sciences (miscellaneous) ,East Asian Monsoon ,Climate model ,Geology ,0105 earth and related environmental sciences - Abstract
Records from natural archives show that the strength of the East Asian summer monsoon (EASM) strongly depends on the orbital configuration of the Earth. However, the dominant orbital cycles driving EASM have been found to be spatially different. Speleothem stable oxygen isotopic records from southern China, which are believed to reflect large-scale changes in the Asian monsoon system, are dominated by climatic precession cycles. Further north, on the Chinese Loess Plateau (CLP), loess-and-paleosol sequences, which are argued to be controlled by monsoon intensity, are in pace with global ice volume changes dominated by obliquity, and after the mid-Pleistocene transition by 100-kyr cycles. To understand these critical discrepancies, here we apply a novel proxy based on the trace metal compositions of pedogenic carbonate in the eolian deposits on the CLP to reconstruct summer precipitation over the last 1.5 million years. Our reconstructions show that summer precipitation on the CLP is dominantly forced by obliquity not in pace with the ice-volume-imprinted loess-paleosol sequences before and after the mid-Pleistocene transition or with the precession-paced speleothem oxygen isotopic records. Coupled with climate model results, we suggest that the obliquity-driven variations of summer precipitation may originate from the gradient of boreal insolation that modulates the thermal contrast between the Asian continent and surrounding oceans.
- Published
- 2017
37. Near zero thermal expansion in Ge-doped Mn 3 GaN compounds
- Author
-
Laifeng Li, Yongjuan Dai, Wei Wang, Rongjin Huang, and Zhonghua Sun
- Subjects
Materials science ,Process Chemistry and Technology ,Doping ,Analytical chemistry ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Manganese ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,01 natural sciences ,Thermal expansion ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Antiperovskite ,chemistry ,Negative thermal expansion ,0103 physical sciences ,X-ray crystallography ,Materials Chemistry ,Ceramics and Composites ,Dilatometer ,010306 general physics ,0210 nano-technology - Abstract
The antiperovskite Mn 3 Ga 1−x Ge x N (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) compounds were prepared by a method of solid-state sintering at 860 °C under a nitrogen atmosphere for 24 h. The Mn 3 Ga 1−x Ge x N compounds were characterized by X-ray diffraction, thermal dilatometer and physical property measurement system (PPMS), respectively. The experimental results indicate that the starting temperature of negative thermal expansion (NTE) is obviously moved toward a higher temperature region with the increase of Ge content. Meanwhile, the absolute value of coefficient of NTE (|α|) decreases continuously. Accordingly, the near zero thermal expansion (ZTE) behavior is explored at an approximate temperature range of 423–475 K for Mn 3 Ga 0.5 Ge 0.5 N. Furthermore, the mechanism of ZTE is also discussed. The present ZTE behavior serves as a valuable example for demonstrating the promise of exploring other potential ZTE materials in the family of antiperovskite manganese nitrides.
- Published
- 2017
38. Experimental study on strain sensitivity of Internal-Tin Nb3Sn superconducting strand based on non-destructive technology
- Author
-
Laifeng Li, Chuanjun Huang, Shen Fuzhi, and Zhang Hengcheng
- Subjects
010302 applied physics ,Superconductivity ,Materials science ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Conductor ,Protein filament ,Brittleness ,chemistry ,Magnet ,0103 physical sciences ,Ultimate tensile strength ,Fracture (geology) ,Electrical and Electronic Engineering ,Composite material ,010306 general physics ,Tin - Abstract
Fracture of brittle filaments plays a crucial role in significant degradation of critical current density of multifilamentary Nb3Sn strand. Recent researches of distribution of filament factures mostly depend on photographic analysis with SEM or TEM. However, it is hard to obtain spatial distribution of filament fractures in the mulitifilamentary Nb3Sn strand. In addition, almost unavoidable filament fracture is introduced during the sample preparation procedure and it causes deviation of filament fracture distribution. X-ray microtomography is a non-invasive, non-destructive method, which allows determination and the discrimination of internal features without destructing the sample. It is widely used as a non-destructive test technology for its high penetrability and high resolution. This present work investigated filament fracture of two types of Nb3Sn strands under different tensile strains by high energy X-ray. The influence of tensile strain on the filament fracture behavior was investigated and the results will be expected to provide reference for optimization of multifilamentary Nb3Sn strand, conductor and magnet design.
- Published
- 2021
39. Study on cryogenic mechanical properties between superconducting wires and resins for MRI superconducting magnet
- Author
-
Shen Fuzhi, Zhang Hengcheng, Yuan Zhou, Sun Wentao, Chuanjun Huang, Laifeng Li, Zhixiong Wu, Linghui Gong, and Rongjin Huang
- Subjects
010302 applied physics ,Superconductivity ,Materials science ,Superconducting wire ,General Physics and Astronomy ,Superconducting magnet ,Epoxy ,Liquid nitrogen ,engineering.material ,01 natural sciences ,Compressive strength ,Condensed Matter::Superconductivity ,visual_art ,0103 physical sciences ,Ultimate tensile strength ,visual_art.visual_art_medium ,Shear strength ,engineering ,General Materials Science ,Composite material ,010306 general physics - Abstract
Superconducting magnet is a key component in magnetic resonance imaging (MRI). In general, vacuum pressure impregnation (VPI) technology is used for insulating system of the superconducting magnet. Performance of the superconducting magnets is affected by the adhesion strength between superconducting wires and resins at cryogenic temperature. In this study, experimental superconducting coil was prepared by modified bisphenol-A type epoxy resin and the VPI technology. Tensile, shear, and compressive properties of the samples cut from the superconducting coil were measured at both room temperature (RT) and liquid nitrogen temperature (77 K), and the bonding properties between the superconducting wire and the resin were discussed. The results show that the resin exhibits low viscosity, long pot life and higher mechanical strength, and it is suitable for impregnating superconducting magnets by VPI technology. Moreover, the shear and compressive strength of the impregnated superconducting magnet at 77 K are significantly higher than that at room temperature, with the increase of 132% in radial compressive strength, 170% in axial compressive strength, 63% in radial shear strength and 70% in axial shear strength, respectively. This study provides references for the design of insulation for superconducting magnet system and the manufacture of insulating materials for MRI superconducting magnets.
- Published
- 2021
40. In-plane low thermal expansion of NiTi via controlled cross rolling
- Author
-
Laifeng Li, Yusuke Onuki, Qiao Li, Zhongzheng Deng, Qingping Sun, and Wei Wang
- Subjects
010302 applied physics ,Materials science ,Polymers and Plastics ,Neutron diffraction ,Metals and Alloys ,02 engineering and technology ,Shape-memory alloy ,021001 nanoscience & nanotechnology ,Span (engineering) ,01 natural sciences ,Thermal expansion ,Electronic, Optical and Magnetic Materials ,In plane ,Nickel titanium ,0103 physical sciences ,Ceramics and Composites ,Crystallite ,Composite material ,0210 nano-technology ,Order of magnitude - Abstract
Shape memory alloy (SMA) sheets processed via unidirectional rolling (UniR) exhibit macroscopic low thermal expansion (TE) over a wide temperature span but only along a certain direction. Here, we use controlled cross rolling (CroR) to achieve in-plane low coefficients of TE (CTEs) of polycrystalline NiTi sheets. It is shown that the in-plane CTEs of a CroRed NiTi sheet with the three-step rolling path (RD-15%, TD-10% and RD-5%) can be reduced close to zero within a very narrow range (-2.7 × 10−6 K−1 to +3.0 × 10−6 K−1) over a large temperature span of 223 K. The obtained in-plane CTEs are an order of magnitude smaller than those of UniRed NiTi sheets and are comparable to that of commercial FeNi Invar alloy (+2.0 × 10−6 K−1). The physical origin of such in-plane low TE is explored through in situ neutron diffraction from 2.3 K to 300 K and a rule-of-mixture theoretical model. It is found that in the CroRed nanostructured NiTi, the in-plane positive TEs of textured B2 and B19’ aggregates are compensated by the in-plane negative TE caused by the continuous formation (vanishing) of { 102 } 〈 U V W 〉 fiber-textured B19’ variants in cooling (heating), thereby leading to the overall in-plane low TE. Such compensation mechanism in CroR can also be used to achieve in-plane low TE of other SMAs.
- Published
- 2021
41. Combustion synthesis of Cu 2 SnSe 3 thermoelectric materials
- Author
-
Jiangtao Li, Guanghua Liu, Kexin Chen, Laifeng Li, Min Zhou, and Yuyang Li
- Subjects
Materials science ,02 engineering and technology ,Energy consumption ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,Combustion ,01 natural sciences ,0104 chemical sciences ,Waste heat recovery unit ,Thermoelectric generator ,Thermal conductivity ,Chemical engineering ,Electrical resistivity and conductivity ,Materials Chemistry ,Ceramics and Composites ,0210 nano-technology ,Porosity - Abstract
Thermoelectric materials are attractive for solar thermal energy conversion and waste heat recovery. The existing methods for fabricating thermoelectric materials involve multi-step processes with considerable time and energy consumption. Here we report a fast and one-step way to prepare thermoelectric materials by gas-pressure or high-gravity assisted combustion synthesis. Dense Cu2SnSe3 samples with a porosity below 2% were prepared from self-sustained combustion reaction of element powders. The electrical conductivity of the Cu2SnSe3 samples was greatly enhanced and the thermal conductivity was reduced by partial substitution of Sn with In. The ZT values of the un-doped and In-doped Cu2SnSe3 samples reached 0.51 and 0.62 at 773 K, respectively, which are comparable to the best results reported for Cu2SnSe3 produced by other methods. Combustion synthesis offers an efficient way to prepare thermoelectric materials with reduced time and energy consumption, which may open up new possibilities for synthesis of thermoelectric materials.
- Published
- 2016
42. Release of celecoxib from a bi-layer biomimetic tendon sheath to prevent tissue adhesion
- Author
-
Wenguo Cui, Shiyang Yu, Hongjiang Ruan, Laifeng Li, Dapeng Fan, Di Wu, Xianyou Zheng, and Cunyi Fan
- Subjects
musculoskeletal diseases ,Materials science ,Tissue Adhesions ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Polyethylene Glycols ,Tendons ,Biomaterials ,chemistry.chemical_compound ,Biomimetic Materials ,Hyaluronic acid ,Ultimate tensile strength ,medicine ,Animals ,Composite material ,Tissue Adhesion ,Adhesion ,021001 nanoscience & nanotechnology ,Electrospinning ,0104 chemical sciences ,Tendon ,Tendon sheath ,medicine.anatomical_structure ,Membrane ,chemistry ,Celecoxib ,Mechanics of Materials ,Lactates ,0210 nano-technology ,Chickens ,Biomedical engineering - Abstract
Posttraumatic tendon adhesion limits the motion of the limbs greatly. Biomimetic tendon sheaths have been developed to promote tendon healing and gliding. However, after introduction of these biomaterials, the associated inflammatory responses can decrease the anti-adhesion effect. Celecoxib is a non-steroidal anti-inflammatory drug (NSAID) that can decrease inflammation responses. We blended hyaluronic acid and poly(l-lactic acid)-polyethylene glycol (PELA) with microgel electrospinning technology to form an inner layer of a bi-layer biomimetic sheath using sequential electrospinning of an outer celecoxib-PELA layer. Electrospun bi-layer fibrous membranes were mechanically tested and characterized by morphology, surface wettability, and drug release. The tensile strength showed a decreased trend and water contact angles were 114.7 ± 3.9°, 103.6 ± 4.4°, 116.3 ± 5.1°, 122.8 ± 4.7°, and 126.5 ± 4.2° for the surface of PELA, hyaluronic acid-PELA, 2, 6, and 10% celecoxib-PELA electrospun fibrous membranes, respectively. In vitro drug release studies confirmed burst release and then sustained release from the fibrous membranes containing celecoxib for 20 days. In a chicken model of flexor digitorum profundus tendon surgery, the outer celecoxib/PELA layer offered advanced anti-adhesion roles compared to the outer PELA layer and the inner hyaluronic acid-loaded PELA layer still offered tendon healing and gliding. Thus, celecoxib-loaded anti-adhesive tendon sheaths can continuously offer bi-layer biomimetic tendon sheath effects with celecoxib release from the outer layer to prevent tendon adhesion.
- Published
- 2016
43. La(Fe, Si, Co)13/Cu conductive composites with tailoring thermal expansion
- Author
-
Xuepu Liu, Chuanjun Huang, Rongjin Huang, Yemao Han, Zengguang Lu, Laifeng Li, and Xinran Shan
- Subjects
Materials science ,business.industry ,Mechanical Engineering ,Metals and Alloys ,Sintering ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Thermal conductivity ,Semiconductor ,Mechanics of Materials ,Phase (matter) ,Thermoelectric effect ,Thermal ,Materials Chemistry ,Microelectronics ,Composite material ,0210 nano-technology ,business - Abstract
In this work, metal-matrix composites which possess tunable thermal expansion coefficients in combination with high electrical and thermal conductivities were successfully synthesized by a moderate temperature hot-pressing method. The composites are based on incorporating La(Fe, Si, Co)13, a material with a negative coefficient of thermal expansion, within a continuous Cu matrix. The La(Fe, Si, Co)13 enables us to tune the coefficient of thermal expansion in a predictable manner, while the Cu phase is responsible for the electrical and thermal conductivity properties. The resulting materials exhibit coefficients of thermal expansion which can be tuned between the value of pure Cu and La(Fe, Si, Co)13. Thus, by adjusting the relative amount of the two components, the materials can be designed with high electrical and thermal conductivities and tailoring coefficient of thermal expansion properties. This unique combination of electrical and thermal properties enables these Cu-based metal-matrix composites to be applied in the microelectronic, semiconductor and thermoelectric industries.
- Published
- 2016
44. Direct fabrication of highly-dense Cu2ZnSnSe4 bulk materials by combustion synthesis for enhanced thermoelectric properties
- Author
-
Laifeng Li, Guanghua Liu, Jiangtao Li, Min Zhou, Yuyang Li, Yemao Han, and Kexin Chen
- Subjects
010302 applied physics ,Materials science ,Fabrication ,Mechanical Engineering ,Sintering ,Nanotechnology ,02 engineering and technology ,Partial substitution ,021001 nanoscience & nanotechnology ,Thermoelectric materials ,Combustion ,01 natural sciences ,Waste heat recovery unit ,Chemical engineering ,Mechanics of Materials ,0103 physical sciences ,Thermoelectric effect ,lcsh:TA401-492 ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,0210 nano-technology ,Porosity - Abstract
Thermoelectric materials are attractive for solar thermal energy conversion and waste heat recovery. The preparation of bulk thermoelectric materials usually involves multi-step processes with considerable time and energy consumption. Here we report an alternative way called combustion synthesis to realize one-step and fast fabrication of bulk Cu2ZnSnSe4 thermoelectric materials. The combustion synthesis was carried out in 2 MPa Ar gas atmosphere or in a high-gravity field in order to reduce the porosity in samples and complete simultaneous densification during synthesis. Nearly full-dense Cu2ZnSnSe4 samples with a porosity of
- Published
- 2016
45. Experimental investigation on the thermal performance of helium based cryogenic pulsating heat pipe
- Author
-
Laifeng Li, Huiming Liu, and Dong Xu
- Subjects
Fluid Flow and Transfer Processes ,Materials science ,020209 energy ,Mechanical Engineering ,General Chemical Engineering ,Thermal resistance ,Aerospace Engineering ,chemistry.chemical_element ,Thermodynamics ,02 engineering and technology ,01 natural sciences ,Heat pipe ,Thermal conductivity ,Nuclear Energy and Engineering ,chemistry ,Latent heat ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Composite material ,010306 general physics ,Lambda point refrigerator ,Condenser (heat transfer) ,Helium ,Evaporator - Abstract
An experimental investigation was conducted to study the thermal performance of a cryogenic pulsating heat pipe (PHP) filled with helium in terms of thermal resistance, effective thermal conductivity and the maximum transferred power. The stainless steel helium PHP in this paper with an inner diameter of 0.5 mm was bent to 8 parallel channels, and the lengths of the evaporator, condenser, and adiabatic section were 50 mm, 50 mm, and 100 mm, respectively. A mechanical–thermal switch worked as a novel pre-cooling system for the helium PHP was developed, which was on during the pre-cooling process and off during the test process. Tests were performed with different heat power, tilt angle and liquid filling ratio. For the helium PHP at +30° with a liquid filling ratio of 70.8%, the effective thermal conductivity was 4800–13,000 W/m K, which was higher than that of copper. With the increment of heat power, the thermal resistance decreased at first and then increased, while the effective thermal conductivities were the opposite. The effective thermal conductivity and the maximum transferred power increased with the increment of the tilt angle. In addition, the helium PHP possessed the optimal liquid filling ratio which could make the maximum thermal conducting effectivity, and the optimal liquid filling ratio changed with the heat power. The optimal liquid ratio, by its very nature, meant reasonable proportion of sensible and latent heat.
- Published
- 2016
46. MCM-41 mesoporous silica sheet with ordered perpendicular nanochannels for protein delivery and the assembly of Ag nanoparticles in catalytic applications
- Author
-
Nanjing Hao, Laifeng Li, and Fangqiong Tang
- Subjects
Materials science ,biology ,Nanotechnology ,Selective catalytic reduction ,General Chemistry ,Mesoporous silica ,Condensed Matter Physics ,Catalysis ,chemistry.chemical_compound ,Mesoporous organosilica ,MCM-41 ,Chemical engineering ,chemistry ,Mechanics of Materials ,biology.protein ,General Materials Science ,Petroleum ether ,Bovine serum albumin ,Microscale chemistry - Abstract
In this study, well-ordered microscale MCM-41 mesoporous silica sheets of ca. 80 nm thicknesses were first prepared by using water and petroleum ether as cosolvents in the presence of CTAB as template and TEOS as silica precursor. The as-synthesized materials showed excellent bovine serum albumin proteins loading capacity (598 mg protein per gram silica materials), controllable sustained protein release profile, and effective catalytic reduction performance of 4-nitrophenol after high payload of Ag nanoparticles.
- Published
- 2015
47. Effect of partial substitution of Ce for La on the structural, magnetic and abnormal thermal expansion properties of La1-Ce Fe11.2Al1.8 alloys
- Author
-
Rongjin Huang, Yemao Han, Hua Zhang, Wei Wang, Jianjun Huang, Jiangang Li, Fukai Zheng, Shibin Guo, Hao Wang, and Laifeng Li
- Subjects
Materials science ,business.industry ,Mechanical Engineering ,Metals and Alloys ,Intermetallic ,Analytical chemistry ,02 engineering and technology ,Atmospheric temperature range ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Inductive coupling ,Thermal expansion ,0104 chemical sciences ,Magnetization ,Negative thermal expansion ,Operating temperature ,Mechanics of Materials ,Materials Chemistry ,Microelectronics ,0210 nano-technology ,business - Abstract
NaZn13-type La(Fe, M)13-based (M = Si, Al) intermetallic compounds find wide applications, ranging from microelectronics to space technology, because of their significant abnormal thermal expansion (ATE) associated with their huge magnetovolume effect. In this work, element La was partially substituted in LaFe11.2Al1.8 by element Ce to optimize the ATE characteristics of these alloys. The obtained average thermal expansion coefficient (CTE) of La0.8Ce0.2Fe11.2Al1.8 reaches as large as −21.7 × 10−6 K−1 in the temperature range of 100–200 K, which is nearly 25% larger than that of LaFe11.2Al1.8 (−17.31 × 10−6 K−1). Magnetic measurements confirmed that the improved negative thermal expansion (NTE) property is attributed to the enhanced magnetization originating from the magnetic coupling between Ce and Fe atoms. Additionally, smaller negative thermal expansion was observed in La0.4Ce0.6Fe11.2Al1.8 with an average CTE of −1.6 × 10−6 K−1 in a broad operating temperature window from 10 to 170 K. The enhanced NTE values of La(Fe, Al)13-based alloys with partial substitution of Ce for La demonstrated in this work show the potential of their practical applications.
- Published
- 2020
48. Evaluation of fatigue crack propagation behavior of 316LN TIG weldments at liquid helium temperature
- Author
-
Yuntao Song, Jijun Xin, Chuanjun Huang, Dong Xu, Zhang Hengcheng, Jing Wei, Laifeng Li, and Rongjin Huang
- Subjects
010302 applied physics ,Materials science ,Liquid helium ,Gas tungsten arc welding ,General Physics and Astronomy ,chemistry.chemical_element ,Transgranular fracture ,Fracture mechanics ,Welding ,Tungsten ,Microstructure ,01 natural sciences ,law.invention ,chemistry ,law ,Martensite ,0103 physical sciences ,General Materials Science ,Composite material ,010306 general physics - Abstract
In the present work, fatigue crack propagation behavior of 316LN tungsten inert gas (TIG) weldment and weldment with post weld heat treatment (PWHT) was investigated at liquid helium temperature. Results indicates that the weldment with PWHT results in the highest fatigue crack propagation resistance, whereas the base material demonstrates the lowest fatigue crack propagation resistance. Microstructure evolution reveals that the fatigue crack propagation is characterized as transgranular fracture for the base material as well as the as-welded weldments and the weldment with PWHT. Moreover, the crack propagation path of the weldments shows a zigzag crack extension, especially for the weldment with PWHT, whereas the crack extension of the base material is relative straight. Electron backscattered diffraction reveals more amount of strain-induced martensite near the crack tip in the base material compared to in the as-welded weldment and in the weldment with PWHT, which is considered to be a crucial factor in the fatigue crack propagation behavior at cryogenic temperature.
- Published
- 2020
49. A comparative study of compositions and microstructures of two types internal-tin process Nb3Sn wires
- Author
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Rongjin Huang, Laifeng Li, Zhang Hengcheng, and Chuanjun Huang
- Subjects
010302 applied physics ,Materials science ,Scanning electron microscope ,Resolution (electron density) ,General Physics and Astronomy ,chemistry.chemical_element ,Microstructure ,01 natural sciences ,Copper ,chemistry ,Transmission electron microscopy ,Phase (matter) ,0103 physical sciences ,General Materials Science ,Selected area diffraction ,Composite material ,010306 general physics ,Tin - Abstract
In the present work, microstructural and microchemical of Nb3Sn strands with the internal tin process produced by the Western Superconductor Technology co., Ltd (WST) and Oxford Instruments co., Ltd (OST) were analyzed. The internal 3D-view of two Nb3Sn strands were detected with a (sub-)micrometric resolution in a non-invasive, non-destructive way, i.e. high-resolution 3D X-ray micro tomography. The distribution of filaments and voids induced by the functional heat treatment of two strands were investigated. The elements distribution after heat reaction of two strands was investigated through elemental mapping by scanning electron microscope (SEM) and energy dispersive X-ray analysis. The filaments of the WST Nb3Sn strand distributed uniformly, whereas the filaments separated with clear copper boundary among filaments. However, the filaments of the OST Nb3Sn strand have serious overlap phenomenon and the copper isolation interface was not clear among filaments. In order to investigate the distinction of microstructure, the selected area electron diffraction was also performed by transmission electron microscopy (TEM) and the results indicated that obvious impurities were observed in the Nb3Sn phase of the WST strand compared to the OST strand.
- Published
- 2020
50. Low-temperature coefficient of resistivity in LaFe13-xSix compounds
- Author
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Hao Wang, Rongjin Huang, and Laifeng Li
- Subjects
010302 applied physics ,Materials science ,Component (thermodynamics) ,Analytical chemistry ,General Physics and Astronomy ,Crystal structure ,01 natural sciences ,Metal ,Tetragonal crystal system ,Electrical resistivity and conductivity ,visual_art ,0103 physical sciences ,Measuring instrument ,visual_art.visual_art_medium ,General Materials Science ,010306 general physics ,Temperature coefficient ,Powder diffraction - Abstract
The resistivity of metal materials usually increases as the temperature rises and the temperature coefficient of resistivity (TCR) could be a few thousand (ppm/K). In fact, this would cause trouble to the accurate measuring instrument used in varying temperature conditions. Thus, it is a great challenge to develop materials with a low-temperature coefficient of resistivity (L-TCR). In this paper, we synthesized LaFe13-xSix compounds showing L-TCR behavior. The X-ray powder diffraction (XRD) patterns revealed that the crystal structure of LaFe13-xSix compounds changes from a cubic structure to a tetragonal structure as the Si component rises, and new phases like LaSi2 and FeSi appear. By testing electrical property, we find that the local extremum of the TCR is obtained in LaFe5Al8 compound, which is −54.4 ppm/K over 5–300 K.
- Published
- 2020
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