挤压态GNS/7075复合材料组织及性能研究

采用光学显微镜和扫描电子显微镜分析了热挤压前后GNS(石墨烯纳米片)/7075铝基复合材料的微观组织的演变,并测试了复合材料的拉伸性能、显微硬度及摩擦磨损性能。研究结果表明:在铝基体中添加GNS可以有效地细化铝基体的晶粒组织,并且对铸态复合材料进行热挤压处理可以有效地消除晶界处元素偏析及GNS偏聚,有利于复合材料微观形貌的改善。挤压态0.9%GNS/7075复合材料的抗拉强度、伸长率及显微硬度分别为379.1 MPa、13.5%和HV174.1,比铸态复合材料分别提高了33.62%、181%和44%。挤压态复合材料的磨损量仅为0.012 g,与7075基体的磨损量(0.025 g)相比减少了0.013 g。7075基体的磨面上存在大区域的犁沟状凹陷和层片状剥落,凹坑数量较多,而挤压态复合材料的磨面上出现了大小不一的犁沟成排分布,犁沟的深度和宽度明显变小,并且零星散落着面积小且深度浅的粘着坑。

Tracking Regulatory Mechanism of Trace Fe on Graphene Electromagnetic Wave Absorption

Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the first time, the reduced graphene oxide(RGO) based absorbers are developed with regulatory absorption properties and the absorption mechanism of RGO is mainly originated from the carrier injection behavior of trace metal Fe nanosheets on graphene. Accordingly, the minimum reflection loss(RLmin) of Fe/RGO-2composite reaches-53.38 dB(2.45 mm), and the effective absorption bandwidth achieves 7.52 GHz(2.62 mm) with lower filling loading of 2 wt%. Using off-axis electron hologram testing combined with simulation calculation and carrier transport property experiments, we demonstrate here the carrier injection behavior from Fe to graphene at the interface and the induced charge accumulation and rearrangement, resulting in the increased interfacial and dipole polarization and the conductance loss. This work has confirmed that regulating the dielectric property of graphene itself by adding trace metals can not only ensure good impedance matching, but also fully exploit the dielectric loss ability of graphene at low filler content,which opens up an efficient way for designing lightweight absorbers and may be extended to other types materials.

Spin-polarized pairing induced by the magnetic field in the Bernal bilayer graphene

Recent experimental findings have demonstrated the occurrence of superconductivity in Bernal bilayer graphene when induced by a magnetic field.In this study,we conduct a theoretical investigation of the potential pairing symmetry within this superconducting system.By developing a theoretical model,we primarily calculate the free energy of the system with p+ip-wave parallel spin pairing,p+ip-wave anti-parallel spin pairing and d+i d-wave pairing symmetry.Our results confirm that the magnetic field is indeed essential for generating the superconductivity.We discover that the p+ip-wave parallel spin pairing leads to a lower free energy for the system.The numerical calculations of the energy band structure,zero-energy spectral function and density of states for each of the three pairing symmetries under consideration show a strong consistency with the free energy results.

Effect of external magnetic field on the instability of THz plasma waves in nanoscale graphene field-effect transistors

The instability of plasma waves in the channel of field-effect transistors will cause the electromagnetic waves with THz frequency.Based on a self-consistent quantum hydrodynamic model,the instability of THz plasmas waves in the channel of graphene field-effect transistors has been investigated with external magnetic field and quantum effects.We analyzed the influence of weak magnetic fields,quantum effects,device size,and temperature on the instability of plasma waves under asymmetric boundary conditions numerically.The results show that the magnetic fields,quantum effects,and the thickness of the dielectric layer between the gate and the channel can increase the radiation frequency.Additionally,we observed that increase in temperature leads to a decrease in both oscillation frequency and instability increment.The numerical results and accompanying images obtained from our simulations provide support for the above conclusions.

Investigation of Acoustomagnetoelectric Effect in Bandgap Graphene by the Boltzmann Transport Equation

We study the acoustomagnetoelectric (AME) effect in two-dimensional graphene with an energy bandgap using the semiclassical Boltzmann transport equation within the hypersound regime, (where represents the acoustic wavenumber and is the mean free path of the electron). The Boltzmann transport equation and other relevant equations were solved analytically to obtain an expression for the AME current density, consisting of longitudinal and Hall components. Our numerical results indicate that both components of the AME current densities display oscillatory behaviour. Furthermore, geometric resonances and Weiss oscillations were each defined using the relationship between the current density and Surface Acoustic Wave (SAW) frequency and the inverse of the applied magnetic field, respectively. Our results show that the AME current density of bandgap graphene, which can be controlled to suit a particular electronic device application, is smaller than that of (gapless) graphene and is therefore, more suited for nanophotonic device applications.

Massive Dirac particles based on gapped graphene with Rosen-Morse potential in a uniform magnetic field

We explore the gapped graphene structure in the two-dimensional plane in the presence of the Rosen-Morse potential and an external uniform magnetic field.In order to describe the corresponding structure,we consider the propagation of electrons in graphene as relativistic fermion quasi-particles,and analyze it by the wave functions of two-component spinors with pseudo-spin symmetry using the Dirac equation.Next,to solve and analyze the Dirac equation,we obtain the eigenvalues and eigenvectors using the Legendre differential equation.After that,we obtain the bounded states of energy depending on the coefficients of Rosen-Morse and magnetic potentials in terms of quantum numbers of principal n and spin-orbit k.Then,the values of the energy spectrum for the ground state and the first excited state are calculated,and the wave functions and the corresponding probabilities are plotted in terms of coordinates r.In what follows,we explore the band structure of gapped graphene by the modified dispersion relation and write it in terms of the two-dimensional wave vectors K_(x) and K_(y).Finally,the energy bands are plotted in terms of the wave vectors K_(x) and K_(y) with and without the magnetic term.

Highly Aligned Graphene Aerogels for Multifunctional Composites

Stemming from the unique in-plane honeycomb lattice structure and the sp^(2)hybridized carbon atoms bonded by exceptionally strong carbon–carbon bonds,graphene exhibits remarkable anisotropic electrical,mechanical,and thermal properties.To maximize the utilization of graphene’s in-plane properties,pre-constructed and aligned structures,such as oriented aerogels,films,and fibers,have been designed.The unique combination of aligned structure,high surface area,excellent electrical conductivity,mechanical stability,thermal conductivity,and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions,enabling advancements in diverse fields.This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites.It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively.The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties,showing enhanced electrical,mechanical,and thermal properties along the alignment at the sacrifice of the perpendicular direction.This review showcases remarkable properties and applications of aligned graphene aerogels and their composites,such as their suitability for electronics,environmental applications,thermal management,and energy storage.Challenges and potential opportunities are proposed to offer new insights into prospects of this material.

基于GNS3的虚拟仿真网络实验室配置与部署

传统网络实验室的硬件成本高,维护和更新费用也高,搭建和修改网络拓扑耗时费力,灵活性较差,空间和资源非常有限,扩展也受到诸多限制,并且在实验过程中的某些错误可能会导致设备的损坏或造成网络故障。同时,学生人数过多也会导致单独使用实验的时间过少,并且无法随时随地进行上机测试或实训,每次进行实验需要重新配置硬件设备,过程既麻烦又浪费时间。为了解决传统网络实验室存在的各种问题,提出一种有效的方法,使用虚拟仿真网络实验室。虚拟仿真网络实验室是利用虚拟仿真结合物理桥接技术模拟各种网络实验的系统平台,可以高效、安全地进行各种网络实验和测试。通过深入研究基于GNS3的虚拟仿真网络实验室的部署方案,为实际应用提供指导和参考。

Ag-GNSs/Sn-Ag-Cu复合钎料焊点的润湿性能及界面生长特征研究

采用Ag涂覆石墨烯纳米片(Ag-GNSs)作为增强体,制备Sn-3.0Ag-0.5Cu-(Ag-GNSs)新型复合无铅钎料,然后在Cu基板上制备了钎料焊点,并进行了150℃不同时长的等温时效处理,研究了不同含量的Ag-GNSs对无铅钎料Sn-3.0Ag-0.5Cu的润湿性、Cu基板/钎料界面金属间化合物(IMC)生长特性的影响。结果表明,适量的Ag-GNSs可以显著地改善钎料的润湿性,当Ag-GNSs含量达到0.05wt%时润湿性最佳,与Sn-3.0Ag-0.5Cu钎料相比润湿角降低了54.43%。随着等温时效时间的延长,IMC层厚度增大,其生长行为由扩散控制。Ag-GNSs的添加可以抑制IMC层的生长,当Ag-GNSs的含量为0.05wt%时扩散系数达到最小值2.356×10^(-18)m^(2)/s。在0~0.2wt%范围内,Ag-GNSs的最佳添加量为0.05wt%。

表达SFTSV Gn基因的重组5型腺病毒的构建与鉴定

为了构建出表达新布尼亚病毒(SFTSV)Gn基因的重组5型腺病毒,试验根据GenBank上发表的SFTSV Gn基因序列(登录号为ADZ04482.1)设计合成引物,采用特异性PCR方法在Gn基因前添加了KOZAK序列和tPA信号肽序列;然后通过酶切、连接等方法构建重组穿梭质粒PGA-KOZAK-tPA-Gn,与腺病毒骨架质粒pAd5-ΔE1ΔE3-5E4在BJ5183感受态细胞中进行同源重组,得到重组腺病毒质粒rAd5-KOZAK-tPA-Gn,用PacⅠ酶酶切重组腺病毒质粒,并将线性化的质粒转染至HEK 293细胞中进行病毒包装、扩繁和纯化;采用PCR扩增、Western-blot等技术检测病毒基因的表达情况,并测定重组腺病毒效价。结果表明:通过PCR扩增获得了1 546 bp的KOZAK-tPA-Gn基因,并成功构建了重组穿梭质粒;SFTSV Gn基因在重组腺病毒传代过程中稳定存在;重组腺病毒在HEK 293细胞中表达出分子量约为61 ku的SFTSV Gn蛋白;测得重组腺病毒效价为1×10^(-7.63)/0.1 mL TCID_(50)。说明试验成功构建出表达SFTSV Gn基因的重组5型腺病毒。

热处理对GNP-Al复合材料显微组织和性能的影响

本文以石墨烯为增强相,采用高能超声辅助铸造法及后续热处理制备了铝基复合材料,并研究石墨烯和热处理对复合材料显微组织、力学性能和耐磨性能的影响。结果表明,石墨烯促进了复合材料晶粒细化,且热处理后Si相进一步细化及圆整。经热处理后复合材料的屈服强度和抗拉强度(245和319MPa)比基体(119和202MPa)分别提高了105.9%、57.9%。磨损试验结果表明,添加石墨烯和T6热处理后复合材料的磨损率最低,磨损机制由剥层磨损转变为磨粒磨损。

GN-g-MAH/PPy多功能PET非织造布的制备及应用

为提高聚酯(PET)非织造布的性能,将导电材料通过表面改性引入PET非织造布,采用单宁酸(TA)作为桥联剂,功能化石墨烯(GN-g-MAH)和聚吡咯(PPy)作为导电功能层,制备得到多功能PET非织造布,并使用SEM、XRD、TG等测试了PET/GN-g-MAH/PPy的微观结构和热稳定性。结果表明:通过循环自组装法及低温化学聚合法成功制备了PET/GN-g-MAH/PPy非织造布,表现出良好的导电性,表面电阻率低至3.11×10^(-2)Ω·m,表面由疏水转变为亲水。基于此,非织造布也表现出优异的电热性能,对其施加3 V驱动电压时,可在20s内产生约40℃的饱和温度。此外,还具有良好的光热转换性能,当光照强度为300 mW/cm^(2)时,照射20 s后,表面温度可稳定到105.8℃,非织造布还表现出优异的光热抗菌性,当大肠杆菌的菌液浓度为1.6×10^(8)CFU/mL时,使用氙灯模拟太阳光源照射后,抗菌率达到99.6%。

Flash‑Induced High‑Throughput Porous Graphene via Synergistic Photo‑Effects for Electromagnetic Interference Shielding

Porous 2D materials with high conductivity and large surface area have been proposed for potential electromagnetic interference(EMI)shielding materials in future mobility and wearable applications to prevent signal noise,transmission inaccuracy,system malfunction,and health hazards.Here,we report on the synthesis of lightweight and flexible flash-induced porous graphene(FPG)with excellent EMI shielding performance.The broad spectrum of pulsed flashlight induces photo-chemical and photo-thermal reactions in polyimide films,forming 5×10 cm^(2)-size porous graphene with a hollow pillar structure in a few milliseconds.The resulting material demonstrated low density(0.0354 g cm^(−3))and outstanding absolute EMI shielding effectiveness of 1.12×10^(5) dB cm^(2) g^(−1).The FPG was characterized via thorough material analyses,and its mechanical durability and flexibility were confirmed by a bending cycle test.Finally,the FPG was utilized in drone and wearable applications,showing effective EMI shielding performance for internal/external EMI in a drone radar system and reducing the specific absorption rate in the human body.

Direct conversion of CO_(2)to graphene via vapor–liquid reaction for magnesium matrix composites with structural and functional properties

Converting CO_(2)to valuable materials is attractive in environmental protection and resource utilization.In this study,a vapor-liquid interface reaction system for mass production of high-quality graphene is reported.The graphene obtained has high crystallinity and few defects during the reaction of CO_(2)and Mg melt.The growth mechanism of graphene is demonstrated in vapor-liquid interface area by combining the CO_(2)bubbles as a soft template to guide growth with the confinement effect of dense MgO nanoparticles.The quality of the graphene is verified by epoxy composites with high electromagnetic shielding effectiveness.Additionally,the V-L reaction method ingeniously solves the dispersion of graphene in metal,providing a preparation strategy of Mg matrix composites with structure and function integration.

Carbon nanotube and graphene reinforced magnesium matrix composites:A state-of-the-art review

Magnesium(Mg)composites reinforced with carbon-based nanomaterial(CBN)often exhibit low density,enhanced strength,good conductivity,improved wear resistance,and excellent biocompatibility when compared to current industry Mg alloys.This review aims to critically evaluate recent developments in Mg-CBN composites and is divided into five sections:First,a brief introduction to Mg-CBN composites is provided,followed by a discussion of different fabrication techniques for these composites,including powder metallurgy,casting,friction stir processing,and selective laser melting.A particular focus is on the current processing challenges,including dispersion strategies to create homogeneous Mg-CBN composites.The effect of processing on the quantifying disorder in CBNs and distinguishing different sp2carbon materials is also highlighted.Then,the effect of CBN on various properties of Mg-CBN composites is thoroughly analyzed,and the strengthening efficiency of CNTs and graphene in the Mg matrix is examined.Finally,the potential applications of Mg-CBN composites in various industries are proposed,followed by a summary and suggestions for future research directions in the field of Mg-CBN composites.

Composites of In/C hexagonal nanorods and graphene nanosheets for high-performance electromagnetic wave absorption

In recent years,electromagnetic wave(EMW)absorption has been extensively investigated for solving EMW radiation and pollution.The metal-organic frameworks(MOFs)have attracted attention due to their low density and unique structure,which can meet the requirements of strong reflection loss(RL)and wide absorption bandwidth of EMW absorption materials.In this manuscript,indium nanoparticles/porous carbon(In/C)nanorods composites were prepared via the pyrolysis of nanorods-like In-MOFs at a low temperature of450°C.Indium nanoparticles are evenly attached and embedded on porous carbon.Low electrical conductivity of In/C nanorods is unfavorable to EMW absorption performance,which is due to the low temperature carbonization.Thus,graphene(Gr)nanosheets with high electrical conductivity are introduced to adjust electromagnetic parameters of In/C nanorods for enhancing EMW absorption.The minimum RL of the In/C-Gr-4 composite is up to-43.7 dB with a thin thickness of 1.30 mm.In addition,when the thickness is further reduced to 1.14 mm,the minimum RL of-39.3 dB at 16.1 GHz and effective absorption bandwidth of 3.7 GHz(from 14.3 to 18.0 GHz)can be achieved.This work indicates that In/C-Gr composites show excellent EMW absorption performance.

四边折弯机基于GNS的多组龙门轴插补控制

在大型金属折弯成型领域,四边折弯机正逐渐发挥着重要作用。为了实现更高的加工精度、更快的加工效率、更大的加工范围,通常使用多组龙门轴来驱动机械装置。本文主要介绍基于固高GNS控制器多组龙门轴控制,并且阐述在总线控制模式下实现两组龙门轴样条插补动作。

Laser-Induced Graphene Conductive Fabric Decorated with Copper Nanoparticles for Electromagnetic Interference Shielding Application

To meet the demands for flexible electromagnetic interference(EMI)shielding materials,a type of conductive fabric is prepared by generating three-dimensional(3D)porous laser-induced graphene(LIG)in situ on the surface of the aramid fabric(AF)and then electroless plating copper.After LIG treatment,the porous AF demonstrates admirable conductivity due to the generation of graphene.The superior surface resistance of the conductive fabric can reach 1.57Ω/sq after copper deposition,and the average EMI shielding effectiveness(SE)can reach 34.3 dB in a frequency range of 8.2 to 12.4 GHz,with the EMW absorption accounting for about 80%.The proposed technology provides a new idea for preparation of flexible EMI shielding materials.

Highly Thermoconductive,Strong Graphene‑Based Composite Films by Eliminating Nanosheets Wrinkles

Graphene-based thermally conductive composites have been proposed as effective thermal management materials for cooling high-power electronic devices.However,when flexible graphene nanosheets are assembled into macroscopic thermally conductive composites,capillary forces induce shrinkage of graphene nanosheets to form wrinkles during solution-based spontaneous drying,which greatly reduces the thermal conductivity of the composites.Herein,graphene nanosheets/aramid nanofiber(GNS/ANF)composite films with high thermal conductivity were prepared by in-plane stretching of GNS/ANF composite hydrogel networks with hydrogen bonds andπ-πinteractions.The in-plane mechanical stretching eliminates graphene nanosheets wrinkles by suppressing inward shrinkage due to capillary forces during drying and achieves a high in-plane orientation of graphene nanosheets,thereby creating a fast in-plane heat transfer channel.The composite films(GNS/ANF-60 wt%)with eliminated graphene nanosheets wrinkles showed a significant increase in thermal conductivity(146 W m^(−1)K^(−1))and tensile strength(207 MPa).The combination of these excellent properties enables the GNS/ANF composite films to be effectively used for cooling flexible LED chips and smartphones,showing promising applications in the thermal management of high-power electronic devices.

Carbon nanocages bridged with graphene enable fast kinetics for dual-carbon lithium-ion capacitors

Lithium-ion capacitors(LICs) combining the advantages of lithium-ion batteries and supercapacitors are considered a promising nextgeneration energy storage device. However, the sluggish kinetics of battery-type anode cannot match the capacitor-type cathode, restricting the development of LICs. Herein, hierarchical carbon framework(HCF) anode material composed of 0D carbon nanocage bridged with 2D graphene network are developed via a template-confined synthesis process. The HCF with nanocage structure reduces the Li^(+) transport path and benefits the rapid Li^(+) migration, while 2D graphene network can promote the electron interconnecting of carbon nanocages. In addition, the doped N atoms in HCF facilitate to the adsorption of ions and enhance the pseudo contribution, thus accelerate the kinetics of the anode. The HCF anode delivers high specific capacity, remarkable rate capability. The LIC pouch-cell based on HCF anode and active HCF(a-HCF) cathode can provide a high energy density of 162 Wh kg^(-1) and a superior power density of 15.8 kW kg^(-1), as well as a long cycling life exceeding 15,000cycles. This study demonstrates that the well-defined design of hierarchical carbon framework by incorporating 0D carbon nanocages and 2D graphene network is an effective strategy to promote LIC anode kinetics and hence boost the LIC electrochemical performance.