• Table of Content
      20 April 2020, Volume 48 Issue 4 Previous Issue    Next Issue
    For Selected: View Abstracts Hide(Show) Pic
    Nano Materials Column
    Preparation of a new two-dimensional nanomaterial MXene and its application progress in energy storage
    A-lei DANG, Cheng-lin FANG, Zhao ZHAO, Ting-kai ZHAO, Tie-hu LI, Hao LI
    2020, 48 (4): 1-14.   DOI: 10.11868/j.issn.1001-4381.2019.000390
    Abstract ( 1896 ( PDF (8981KB)( 968 Citation

    As a new type of two-dimensional nanomaterials, MXene has been widely investigated since its discovery at 2011 due to its excellent physical and chemical properties, such as high conductivity, good lubricity, electromagnetism and other special properties. Hence, in addition to the performance of the traditional two-dimensional materials, MXene has been extensively used in the fields of energy storage, catalysis, lubrication, electromagnetic shielding, sensor, water purification and so on, and certain results and progress were achieved. The latest researches of MXene at structure, property and preparation methods, as well as the related achievements in lithium ion battery, supercapacitor and others at our country and overseas in recent years were reviewed in this paper. Moreover, the shortcomings of current research were summarized, and the future research direction were prospected as well.

    Figures and Tables | References | Related Articles | Metrics
    Self-assembly of nanoparticles for lithium-ion battery applications
    Le-hao LIU, Jin-shan MO, Mei-cheng LI, Ting-kai ZHAO, Tie-hu LI, Da-wei WANG
    2020, 48 (4): 15-24.   DOI: 10.11868/j.issn.1001-4381.2019.000593
    Abstract ( 912 ( PDF (3910KB)( 367 Citation

    The physical/chemical properties and synthesis methods of nanoparticles were briefly introduced, and then the type and principle of the self-assembly of nanoparticles were discussed in detail. The research progress in the application of the nanoparticle self-assembly in lithium-ion batteries was summarized, and the existing problems such as the low production efficiency and high pollution in this field were also pointed out. The future works will be focused on developing approp-riate building blocks, disclosing the self-organization mechanisms and simplifying the fabrication processes, and the simultaneous yet effective adjustion of the self-assembly processes in the materials synthesis stage for advanced battery components with hierarchical structures or functions is one of the most important approaches.

    Figures and Tables | References | Related Articles | Metrics
    Research progress on carbon nano-materials to construct Li-ion and Li-S batteries of high performance
    Yi-fang WU, Shao-kun CHONG, Yong-ning LIU, Sheng-wu GUO, Li-feng BAI, Cui-ping ZHANG, Cheng-shan LI
    2020, 48 (4): 25-35.   DOI: 10.11868/j.issn.1001-4381.2019.000590
    Abstract ( 1336 ( PDF (5426KB)( 684 Citation

    Carbon solely can form a lot of nanostructures, such as zero-dimensional nanosphere, one-dimensional nanotube and two-dimensional graphene. They perform differently in Li-ion and Li-S batteries. It is worth noting that CNTs and graphene are not appropriate to be used as electroactive materials for Li-ion or Li-S batteries for four reasons. First, when CNTs and graphene are used as an anode, they often exhibit high specific capacities during the first lithiation step, but a large fraction of lithium ions is irreversibly consumed instead of reversibly stored, leading to a low Coulombic efficiency of the cell. Second, a graphene-based anode has a large voltage hysteresis in the charge/discharge curves. Third, it has been reported a CNT-based anode lacks a steady voltage plateau with large change in voltage during discharge. Fourth, despite their high initial capacities, graphene and CNT-based anodes often suffer from fast capacity decay after a few tens of cycles. Continuous efforts have been made to build better lithium batteries with a higher energy density and wider applicability, including both current state-of-the-art Li-ion batteries and near-term Li-S batteries. Because the behavior of a rechargeable battery is mainly based on the performance of its anode and cathode, designing advanced electrode materials as well as electrode with tailored compositions and structures has been the hot topic in recent years. The role of carbon nano-materials to construct electrode materials and tailored electrodes in Li-ion and Li-S batteries in high performance was reviewed in the paper from three aspects. Firstly, the role of carbon nano-materials in modifying the electroactive materials was discussed from three aspects:electron- and ion-transport facilitators, immobilization sites and volume expansion buffering. Secondly, the role of carbon nano-materials in optimizing the inactive components was considered as follows:conducting additives, current collectors and conductive interlayers. Thirdly, the role of carbon nano-materials in designing the bendable and stretchable devices are discussed from three aspects:conductive phases in nonconductive substrates, flexible current collectors and freestanding composite electrode. Finally, perspectives on future development of Li-ion and Li-S batteries were presented. It is considered that multi-functional carbon nano-materials will be main research focus in the future.

    Figures and Tables | References | Related Articles | Metrics
    Adjusting of multicolor fluorescence carbon dots and their application
    Xing-hua LIU, Jun-li WANG, Ya-ling WANG, Li ZHANG, Yong-zhen YANG, Xu-guang LIU
    2020, 48 (4): 36-45.   DOI: 10.11868/j.issn.1001-4381.2019.000592
    Abstract ( 694 ( PDF (4664KB)( 359 Citation

    Carbon dots(CDs) have attracted extensive attention of researchers because of their excellent fluorescence performance, low toxicity, extensive raw materials and good biocompatibility.However, the emission wavelengths of most CDs are in short-wavelength region of blue and green light, limiting their widespread application.The synthesis of multicolor CDs can guide the realization of long wavelength CDs and broaden the application of CDs.Therefore, the multicolor emitting mechanism of CDs from sizes, inner structures and surface states of CDs was reviewed, the adjusting measures of achieving multicolor CDs were presented, including raw materials, reaction conditions, surface modification, and separation and purification.Furthermore, the application of multicolor CDs in light emitting diode and bioimaging was also summarized.

    Figures and Tables | References | Related Articles | Metrics
    Research progress in nanofluids with graphene addition
    Ming-jie BAI, Jin-long LIU, Zhi-na QI, Jiang HE, Jun-jun WEI, Jian-yin MIAO, Cheng-ming LI
    2020, 48 (4): 46-59.   DOI: 10.11868/j.issn.1001-4381.2019.000194
    Abstract ( 994 ( PDF (2606KB)( 378 Citation

    Lubrication and cooling are two important issues in the current industrial field. The former is of great significance to the energy consumption caused by friction, which is directly related to the service reliability and life of the components in the mechanical field. The latter is very important for the management and application of the final generation of thermal energy in the process of energy conversion.Combination of them exists widely in fields such as aerospace, automobile machinery, etc.Addition of nano-materials into working fluid can not only significantly improve the thermal conductivity of heat transfer fluids, but also achieve anti-wear and lubrication of mechanical parts, showing excellent mechanical and thermal comprehensive properties. Nanofluids are a good working medium for both aspects.In this paper, in view of the hotspot of graphene nanofluids, the theoretical basis and method of dispersion of graphene nanofluids were reviewed, and the factors affecting the suspension stability of graphene nanofluids were investigated.The thermal conductivity mechanism, the influencing factors and the current progress of graphene nanofluids were analyzed. The main reasons for the non-large-scale application of nanofluids were analyzed. The progress of graphene as an additive in the field of lubrication was reviewed. Finally, the application design of graphene nanofluid synergistically enhanced heat transfer and antifriction lubrication was proposed. In the current spacecraft and other applications, due to the lack of extensive research on the thermal mechanical coupling performance of graphene nanofluids and the stability of spacecraft and long-term operational reliability, future research should be based on the current aerospace heat transfer medium and focus on the targeted design of nanoparticles.The research on dynamic flow heat transfer performance and loop life based on space environment should be carried out, which will lay a theoretical foundation and provide technical support for the future application of nanofluids in the spacecrafts.

    Figures and Tables | References | Related Articles | Metrics
    Progress in molecular imprinted photonic crystals
    Xiao-hui WANG, Gong CHEN, Zhi-qiang DONG, Zhi-gang ZHU, Cheng CHEN
    2020, 48 (4): 60-72.   DOI: 10.11868/j.issn.1001-4381.2019.000539
    Abstract ( 762 ( PDF (4453KB)( 433 Citation

    Photonic crystal is a kind of ordered material which consists of two or more periodic arranged refractive index materials, and the propagation of light can be controlled by changing its average refractive index or lattice spacing. The molecularly imprinted photonic crystal chemical sensors based on the combination of responsive photonic crystal structure and molecular imprinting technique have attracted research interests due to their strong specificity, high sensitivity and self-expression ability, which also provide a novel strategy for the trace detection. In this review, the two- and three-dimensional photonic crystal sensor materials were introduced, and the preparation, properties and applications of molecular imprinted photonic crystal(MIPC) were reviewed. The future research focus such as the improvement of resolution and repeatability of MIPC visual detection materials was analyzed and prospected at last.

    Figures and Tables | References | Related Articles | Metrics
    Self-healing polymer hydrogel based on dynamic chemical bonds
    Bing-na HOU, Hui-ling SHEN, Jin LI, Wang-qiang XIE, Zheng-zheng LI
    2020, 48 (4): 73-82.   DOI: 10.11868/j.issn.1001-4381.2019.000698
    Abstract ( 1390 ( PDF (4352KB)( 1031 Citation

    Polymer hydrogel is a soft material with a three-dimensional network structure that can absorb and retain a large amount of water. Polymer hydrogels have good biocompatibility, mechanical properties and important application value in biomedical and bioengineering fields. Self-healing hydrogels are smart hydrogels that respond to external stimuli and repair their own damage. Compared with the traditional hydrogel, the self-healing hydrogel has the property of repairing damage, and received extensive attention in the scientific field in recent years. Dynamic chemistry-based self-healing hydrogels are novel self-healing hydrogels that can reshape three-dimensional network structures by dynamic covalent or non-covalent bonding to repair damage. The new self-healing hydrogel can quickly repair its own damage and has good environmental adaptability, laying the foundation for the development of self-healing hydrogels as multifunctional new materials. The research progress of recent self-healing hydrogels based on dynamic chemistry was reviewed in this paper, especially focusing on the updated development on self-healing hydrogels based on hydrogen bonds, metal coordination interactions, host-guest interactions, ionic bonds, hydrophobic interactions, imine bonds/acylhydrazone bonds, borate bonds and disulphide bonds, and meanwhile, the problem of self-healing hydrogels was put forward, and the future direction of development was finally predicted.

    Figures and Tables | References | Related Articles | Metrics
    Research progress in stannous oxide thin film transistors
    Pei-miao DENG, Hong-long NING, Wei-guang XIE, Xian-zhe LIU, Yu-xi DENG, Ri-hui YAO, Jun-biao PENG
    2020, 48 (4): 83-88.   DOI: 10.11868/j.issn.1001-4381.2019.000065
    Abstract ( 708 ( PDF (1341KB)( 298 Citation

    Due to its unique optical and electrical properties, p-type metal oxide materials stannous oxide has been favored by more and more people in various fields such as catalysis, sensing and optoelectronic devices.This paper focuses on the research and application of stannous oxide in thin film transistors. As a core component of display driver panels, thin film transistors play an important role in the display.The research progress of p-type stannous oxide thin film transistors was summarized in this paper, which includes the analysis of the microcosmic properties of stannous oxide, the preparation of stannous oxide thin film materials and the fabrication methods of transistors. By introducing the crystal and electronic structure of stannous oxide in details, the microcosmic regul-ation mechanism of the properties of tin oxide was discussed. Through the preparation of stannous oxide materials and the research and application of the devices, the problems of low current-to-switch ratio faced by stannous oxide thin film transistors were analyzed and their prospects in the direction of the complementary metal-oxide-semiconductor devices were put forward, in order to provide a refere-nce for the preparation of p-type metal oxide thin film transistors which are stable and eco-friendly.

    Figures and Tables | References | Related Articles | Metrics
    Liquid metal embrittlement of galvanized steel and its performance during resistance spot welding
    Ting CHEN, Zhan-xiang LING, Min WANG, Liang KONG
    2020, 48 (4): 89-99.   DOI: 10.11868/j.issn.1001-4381.2019.000657
    Abstract ( 969 ( PDF (5069KB)( 537 Citation

    Liquid metal embrittlement is a phenomenon that when a solid metal or alloy with toughness is in direct contact with a liquid metal and a tensile stress is applied, its plasticity decreases and brittle fracture occurs. Liquid metal embrittlement occurs in steels when in contact with liquid zinc, which has been confirmed in the hot tensile test of galvanized steel. In addition, researchers have found that liquid metal embrittlement may also occur during the resistance spot welding of galvanized high-strength steels. It appears that there are a large number of cracks on the surface of the weld spots. These cracks are potentially harmful to the performance of joints. The hot tensile test of the liquid metal embrittlement of galvanized steel was reviewed, the experimental factors that affect the liquid metal embrittlement were clarified, the research progress of liquid metal embrittlement in galvanized steel during resistance spot welding was summarized, and the location of cracks and its influencing factors were analyzed, and possible solutions were summarized.

    Figures and Tables | References | Related Articles | Metrics
    Research Article
    First principles study on geometry structure, elastic property and electronic structure of La-doped Mg2Si
    Ying-min LI, Ming-tan MA, Yu-yan REN, Tong-yu LIU
    2020, 48 (4): 100-107.   DOI: 10.11868/j.issn.1001-4381.2019.000153
    Abstract ( 793 ( PDF (2500KB)( 262 Citation

    The geometrical structure, elastic properties and electronic structure of Mg2Si doped with lanthanum (La) were calculated and analyzed by using the first-principles plane wave pseudopotential method of density functional theory. Firstly, combined with the results of the formation of erbium and Born mechanical stability, it can be seen that Mg8Si4La and Mg8Si3La do not exist stably after doping with rare earth element La. La-doped Mg2Si preferentially occupies the position of the system Mg atom; Secondly, the bulk modulus (B), the shear modulus (G), Young's modulus (E), Poisson's ratio (ν), and anisotropy coefficient (A) of the crystal were calculated that the intrinsic Mg2Si is a brittle phase, while Mg7Si4La is a ductile phase. The doping of La can improve the ductility of Mg2Si. Finally, the calculation of density of states, Mulliken population and charge differential density show that Fermi surface is deviated from the high-energy region after doping with rare earth, and enters the conduction band, which improves the conductivity of Mg2Si.

    Figures and Tables | References | Related Articles | Metrics
    Tensile behavior and plastic deformation mechanism of SiCp/AZ91D magnesium matrix nanocomposites at room temperature
    Cong-yang ZHANG, Zhi-rui LI, dong FANG, Yong-sheng YE, Xi-cong YE, Hai-hua WU
    2020, 48 (4): 108-115.   DOI: 10.11868/j.issn.1001-4381.2019.000665
    Abstract ( 722 ( PDF (3153KB)( 183 Citation

    To obtain magnesium matrix composites with high strength and high plasticity, SiCp/AZ91D magnesium matrix nanocomposites with uniform dispersion of SiC nanoparticles were prepared by high intensity ultrasonic dispersion method and metal mold gravity casting process, following by T4 solution heat treatment and the tensile test at room temperature. The microstructure and plastic deformation mechanism of the specimen after tensile test were investigated by scanning electron microscope and transmission electron microscope. The results show that the tensile strength and elongation of nanocomposites reach up to 296 MPa and 17.3% at room temperature, respectively. A large number of twins and slip are observed in SiCp/AZ91D magnesium matrix nanocomposites with T4 state after tensile deformation at room temperature. It is obvious that twinning and slip are the main mechanisms of plastic deformation in the nanocomposites.High strain zones are formed around SiC nanoparticles in the α-Mg matrix during the tensile process at room temperature, and a lot of dislocations and stacking faults are formed in the high strain zones. These dislocations and stacking faults are evolved into a large number of slip bands and twins under the action of tensile strain, which is the plastic deformation mechanism of SiCp/AZ91D magnesium matrix nanocomposites with high plasticity at room temperature.

    Figures and Tables | References | Related Articles | Metrics
    Dissolution behavior of second phases in 7050 aluminum alloy
    Ya LI, Yun-lai DENG, Jin ZHANG, Ai-qin TIAN, Yong ZHANG
    2020, 48 (4): 116-122.   DOI: 10.11868/j.issn.1001-4381.2019.000742
    Abstract ( 808 ( PDF (4133KB)( 313 Citation

    The dissolution behavior of equilibrium η(MgZn2), T(Al2Mg3Zn3), S(Al2CuMg) and Fe-containing Al7Cu2Fe insoluble phases of hot rolled 7050 aluminum alloy during solid solution treatment was studied. The dissolution kinetics data of the equilibrium phases were obtained by means of in-situ scanning electron microscope tissue detection method. On the basis of bulk diffusion controlled dissolution kinetics models, the effects of curvature and interfacial reaction on atomic migration rate were introduced, and the dissolution kinetics models of η, T and S phases were established. The results show that η and T phases of 7050 aluminum alloy can be completely dissolved within 2 min at the usual solution temperature (470℃); it takes a long time for S phase to completely dissolve, while the Fe-containing phase hardly dissolves; the curvature has little effect on the phase dissolution, but the dissolution rate can be greatly reduced by the interfacial reaction. The predicted results of the second-phase dissolution kinetics models are in good agreement with the measured results, such as η, T and S phase, which can provide guidance for optimizing the solid solution process of Al-Zn-Mg-Cu alloy.

    Figures and Tables | References | Related Articles | Metrics
    Deformation uniformity of 2219 aluminum alloy thin-walled curved parts in stretch forming process
    Li-hui AN, Shi-jian YUAN
    2020, 48 (4): 123-130.   DOI: 10.11868/j.issn.1001-4381.2019.000042
    Abstract ( 657 ( PDF (5337KB)( 263 Citation

    In order to improve the deformation uniformity of stretch formed 2219 aluminum alloy thin-walled curved parts, the finite element model based on Hill 1990 anisotropic yield criterion was established and their strain distribution was simulated numerically by using the ABAQUS software. On this basis, the effects of loading path and blank shape on the uniformity of stretching deformation were analysed. Results show that both of the loading path and the blank shape have great influence on the deformation uniformity of the curved parts. If the zigzag paths are used, the 2219 aluminum alloy sheet is compressed at the beginning of loading until it becomes to be a certain arch. In this case, not only the rupture tendency near the left clamp can be alleviated, but also the deformation on the right side of the curved part can increase, so as the deformation uniformity can be improved. Moreover, the deformation uniformity can also be improved by reducing the sheet width where the deformation is insufficient. For example, the sheet with small size in the middle or the trapezoid sheet with larger size in left is recommended. In this case, the stress increases in the narrow area during the stretching process, which makes it undergo greater deformation. In the end, the high performance 2219 aluminum alloy curved parts with good surface quality are obtained by stretch forming of rectangular sheet under a zigzag path.

    Figures and Tables | References | Related Articles | Metrics
    Effects of post-weld heat treatment on microstructures and mechanical properties of AA7204-T4 aluminum alloy FSW joint
    Yun-lai DENG, Shu-hao DENG, Ling-ying YE, Sen LIN, Lin SUN, Hua JI
    2020, 48 (4): 131-138.   DOI: 10.11868/j.issn.1001-4381.2018.001373
    Abstract ( 760 ( PDF (5411KB)( 235 Citation

    AA7204-T4 aluminum alloy plates were welded by friction stir welding(FSW), and the effect of post-weld heat treatment on the microstructure and mechanical properties of the FSW joints were studied. The results show that the average grain size(AGS) and recrystallization fraction of nugget zone(NZ) are 4.7 μm and 81.9% in as-welded(AW) treatment, 4.8 μm and 82.4% under the post-weld artificial aging(AA) treatment, 5.9 μm and 86.5% under the heat treatment of solid solution followed by artificial aging(SAA), respectively. The grain structure of NZ is not obviously affected by AA treatment, and the AGS and recrystallization fraction of NZ increase by 25.5% and 5.6% under SAA treatment. The ultimate tensile strength(UTS) of the FSW joints are 296.6, 318.2, 357.4 MPa under the heat treatments of AW, AA and SAA, respectively. The improvement of the mechanical properties of FSW joints is limited by AA treatment, while that can be effectively improved by SAA treatment which leads to the welding coefficient reaching 92.0%. Additionally, the microcracks tend to generate on the "S" line under the effect of water quenching after solid solution, which would lead to the fracture location at this zone and the serious decrease of the elongation.

    Figures and Tables | References | Related Articles | Metrics
    Flexible Si/carbon nanotubes/cellulose composite anodes without adhesive and its electrochemical properties
    Xu LI, Xiao-gang SUN, Jie WANG, Wei CHEN, Ya-pan HUANG, Guo-dong LIANG, Cheng-cheng WEI, Hao HU
    2020, 48 (4): 139-144.   DOI: 10.11868/j.issn.1001-4381.2018.000383
    Abstract ( 702 ( PDF (2482KB)( 229 Citation

    Silicon/carbon composite materials were widely considered as the next generation and the most potential anode materials. In order to reduce the huge expansion of silicon, avoid silicon nanoparticle powder and improve the electrochemical performance of silicon based lithium ion battery, a microporous structure paper of multiwalled carbon nanotubes(MWCNTs) was prepared, and the Si/MWCNTs/cellulose composite flexible lithium ion battery anode was prepared by embedding nanoscale silicon. FESEM shows that the nano-silicons are evenly inserted in the three-dimensional conductive network constructed by MWCNTs. This results in decreased interface resistance owing to increasing contact area between silicon and MWCNTs. The high hole of the anode provides enough space for expansion of silicon in cycles. So, the structural stability and chemical stability of the electrodes significantly are guaranteed. Electrochemical tests demonstrate that the first discharge capacity reaches 2024 mAh/g, and the capacity is still maintained at 850 mAh/g after 30 cycles, which shows good cyclic stability and high specific capacity. The unique electrodes show excellent electrochemical performance. The fabrication process of the electrode is much simpler than traditional coating process, strong maneuverability and a satisfactory prospect for industrial applications.

    Figures and Tables | References | Related Articles | Metrics
    Fabrication and piezoresistance of high temperature ITO thin film strain gauge
    Shen-yong YANG, Cong-chun ZHANG, Zhuo-qing YANG, Hong-fang LI, Jin-yuan YAO, Man-guo HUANG, Hong WANG, Gui-fu DING
    2020, 48 (4): 145-150.   DOI: 10.11868/j.issn.1001-4381.2018.000875
    Abstract ( 640 ( PDF (2769KB)( 309 Citation

    High temperature thin film strain gauges are widely used in the strain measurement of extreme conditions, especially in the high temperature components. ITO thin film strain gauges can generally be applied to the strain measurements above 1000℃. ITO high temperature thin film strain gauge was fabricated on the ceramic substrate using magnetron sputtering, and then was thermal treated at high temperature in pure N2 atmosphere, with the purpose of studying its microstructure, XPS, temperature resistance characteristics and piezoresistive response. The results show that the temperature coefficient of resistance (TCR) of ITO thin film strain gauge can stabilize at -750×10-6-1. In addition, ITO thin film strain gauge is loaded at 1200℃, and the results show that the drift rate is 0.0018 h-1 and the strain factor is 16. Stable TCR and low drift rate of ITO thin film strain gauge provide the possibility for its application in the strain measurement of the hot end components.

    Figures and Tables | References | Related Articles | Metrics
    Thermal performance prediction and verification of 2D triaxial braided composites based on coupling method
    Fang-fang ZHANG, Yong-chuan DUAN, An-na GAO, Dan YAO
    2020, 48 (4): 151-157.   DOI: 10.11868/j.issn.1001-4381.2019.000776
    Abstract ( 656 ( PDF (3727KB)( 193 Citation

    In order to improve the shortcomings of the finite element unit-cell establish method based on traditional FEM, which has difficulty in meshing and calculation, a superimposed method was proposed. Based on the superimposed method, the finite element unit-cell model of two-dimensional triaxial braided composites was established. Based on the coupling method, the coordination relationship between degree of freedom of element grid of displacement field and temperature field from reinforcement and matrix were given, and the match method of superimposed region thermal properties and the periodic boundary conditions of the unit-cell model temperature field were determined. The equivalent thermal conductivity coefficient and the equivalent thermal expansion coefficient of the unit-cell model were obtained by applying the periodic boundary conditions. Based on this method, the thermal properties of two-dimensional triaxial braided composites were predicted and analysed. The results show that different braiding angles and fiber volume faction have certain effects on the thermal conductivity coefficient and thermal expansion coefficient in different directions.

    Figures and Tables | References | Related Articles | Metrics
    Influence of activated attapulgite on synthesis and pore structure of hierarchical zeolite
    Hong-ji LI, Fa-liang WANG, Xiang LI, Jing YANG, Jing-hua SONG, Bo LI
    2020, 48 (4): 158-164.   DOI: 10.11868/j.issn.1001-4381.2019.000905
    Abstract ( 536 ( PDF (3256KB)( 174 Citation

    Hierarchical zeolite was successfully synthesized with activated attapulgite by the template of TEAOH in one pot. The influence of the activated attapulgite on hierarchical pore structure and crystal morphology of products under the different Si/Al ratios was systematically investigated. The results show that there are obvious diversity of the crystal morphology while the different activated palygorskites as precursors; XRD reveal that ZSM-5, ZSM-12 and ZSM-11 molecular sieves are obtained under the same condition when the alkali-roasted and acid-microwaved attapulgite (HM-NC-ATP), acid-microwaved attapulgite (HM-ATP) and acid-hydrothermal attapulgite (HH-ATP) are the precursors, respectively, and the morphology and pore structure of the products are inconsistent at different Si/Al ratios. Moreover, the hierarchy factor (HF) has a good linear dependence on the Si/Al ratio when HM-NC-ATP and HH-ATP are as the precursor; Hierarchical factor of zeolites is 0.105, which are prepared with HM-ATP, exhibiting the mainly mesoporous structure, it shows that the precursor of HM-ATP is beneficial to the formation of mesoporous structure.

    Figures and Tables | References | Related Articles | Metrics
    Regulation of thermal relaxation behavior and aggregation structure of polyacrylonitrile fiber
    Chen KANG, Tan LIU, Shuai WU, Ya-xian ZHAO, Liang-hua XU
    2020, 48 (4): 165-171.   DOI: 10.11868/j.issn.1001-4381.2017.001600
    Abstract ( 554 ( PDF (2364KB)( 206 Citation

    Polyacrylonitrile (PAN) fibers which formed high-elastic deformation during the spinning process, have thermal relaxation behavior in the heat conditions, such as thermal shrinkage with disorientation. The thermal relaxation behavior of PAN fibers was investigated by thermomechanical analyzer (TMA), dynamic mechanical analyzer (DMA), wide-angle X-ray diffraction(WAXD).And PAN fibers aggregation structure changed by tension and temperature were analyzed. The results show that the forced high-elastic deformation in PAN fibers accounts for more than 10% which leads to disorientation at high temperature. With structure rearrangement under controlled conditions, the high-elastic deformation in PAN fibers can be transferred to plastic deformation by appropriate tension and temperature imposed to fibers without orientation structure loss. By imposing tension and temperature, further improvement is achieved in the regularity of aggregation structure and the orientation of the molecular chain, crystalline structure, and dimensional stability increase by more than 50%. The crystallites of PAN based carbon fibers treated by this method are more regularly arranged along the molecular chain, and the performance has been improved effectively.

    Figures and Tables | References | Related Articles | Metrics