表面改性对螺旋碳纳米管/环氧树脂复合材料力学性能的影响

螺旋碳纳米管(HCNTs)由于其独特的三维螺旋形态及碳纳米管结构可望在新型功能和高强度复合材料领域发挥重要作用。文中研究了不同方式的HCNTs表面改性对环氧树脂复合材料力学性能的影响,并进一步分析了其强韧化机理。研究表明,通过γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)或聚乙烯亚胺(PEI)对HCNTs进行表面改性后与环氧树脂(EP)共混,能够显著提高复合材料的力学性能。KH560改性的HCNTs/EP复合材料冲击强度和拉伸强度分别提高了118. 4%与54. 1%; PEI改性的HCNTs/EP复合材料冲击强度和拉伸强度分别提高了101. 3%与70. 0%。分析认为,表面改性能够改善HCNTs与环氧树脂之间的界面相互作用,有利于两者之间的应力传递,从而使其力学性能得到进一步提高。

Machine learning in materials design:Algorithm and application

Traditional materials discovery is in ‘trial-and-error’ mode, leading to the issues of low-efficiency, high-cost, and unsustainability in materials design. Meanwhile, numerous experimental and computational trials accumulate enormous quantities of data with multi-dimensionality and complexity, which might bury critical ‘structure–properties’ rules yet unfortunately not well explored. Machine learning(ML), as a burgeoning approach in materials science, may dig out the hidden structure–properties relationship from materials bigdata, therefore, has recently garnered much attention in materials science. In this review, we try to shortly summarize recent research progress in this field, following the ML paradigm:(i) data acquisition →(ii) feature engineering →(iii) algorithm →(iv) ML model →(v) model evaluation →(vi) application. In section of application, we summarize recent work by following the ‘material science tetrahedron’:(i) structure and composition →(ii) property →(iii) synthesis →(iv) characterization, in order to reveal the quantitative structure–property relationship and provide inverse design countermeasures. In addition, the concurrent challenges encompassing data quality and quantity, model interpretability and generalizability, have also been discussed. This review intends to provide a preliminary overview of ML from basic algorithms to applications.

Review on Fabrication Methods of in situ Metal Matrix Composites

This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine and thermodynamically stable reinforcing ceramic phase within a metal matrix. As a result, this provides thermodynamic compatibility at the matrix-reinforcement interface. The reinforcement surfaces are also likely to be free of contamination and, therefore, a stronger matrix-dispersion bond can be achieved. Some of these technologies including DIMOX^? XD, PRIMEX^? reactive gas infiltration, high-temperature self-propagating synthesis (SHS), and liquid-solid, or solid-gas-liquid reactions as well as plasma in situ MMCs are expressed in this paper.

Design of novel RGO/2D strip-like ZIF-8/DMAOP ternary hybrid structure towards high-efficiency microwave absorption, active and passive anti-corrosion, and synergistic antibacterial performance

In order to meet the requirements of the marine environment for microwave absorption(MA)materials,we put forward the strategy of constructing multi-functional composite materials,which integrate microwave absorption,anti-corrosion,and antibacterial properties.Herein,graphene oxide(GO)was used as a template to induce the growth of zeolitic imidazolate framework-8(ZIF-8),simultaneously as a two-dimensional(2D)nanocontainers to load corrosion inhibitors to achieve pH-responsive and self-healing properties.Finally,quaternary ammonium salt(dimethyl octadecyl(3-trimethoxylsilyl propyl)ammonium chloride(DMAOP))and sodium ascorbate(VCNa)were introduced to achieve synergistic antibacterial activity and the reduction of GO.The 2D strip-like structure of ZIF-8 was due to the confined growth induced by the electrostatic attraction between ZIF-8 and GO sheets.The as-obtained reduced GO(RGO)/ZIF-8/DMAOP5 exhibited excellent microwave absorption(MA)properties,with a minimum reflection loss(RL)value of-47.08 dB at 12.73 GHz when the thickness was 2.8 mm.Moreover,the effective absorption bandwidth reached 6.84 GHz.After soaking in 3.5%NaCl solution for 35 days,the RGO/ZIF-8/DMAOP5-0.7%coating still achieved an impedance value of 4.585×107Ω·cm^(2) and a protective efficiency of 99.994%,providing superior anti-corrosion properties.In addition,fantastic antibacterial activity was obtained,with the antibacterial rates of RGO/ZIF-8/DMAOP_(10) reaching 99.39%and 100%against Escherichia coli and Staphylococcus aureus.This work could open new avenues towards the development of a new generation of multifunctional MA materials.

Flexible MXene/sodium alginate composite fabric with high structural stability and oxidation resistance for electromagnetic interference shielding

Wearable electromagnetic interference(EMI)shielding fabrics with excellent electromagnetic shielding performance,oxidation resistance,and structural stability are highly demanded for the rapid development of electronic devices and wireless communication.MXenes are metallic conductive materials with exceptional EMI shielding properties,but they are prone to oxidation in air and have poor structural stability and durability on fabric substrates.Herein,we present a one-step assembly method to fabricate fabrics coated with MXenes and polymeric sodium alginate(SA)composite(MXene-SA).SA protects MXenes from oxidation and forms a stable interlayer structure by bonding to MXenes.The MXene-SA coated fabrics are breathable and flexible,and have a low sheet resistance of 2.12±0.08Ω/sq and a high EMI shielding performance of 37.05 dB at X-band,which is comparable to the best 42.31 dB.Moreover,the MXene-SA coated fabrics exhibit high structural stability and oxidation resistance under various conditions of sonication disintegration,mechanical abuse,chemical corrosion,and humidity,compared to pure MXenes coated fabrics.We believe that the wearable and high-performance MXene-SA fabrics have great potential for the next generation of ultra-portable and wearable EMI shielding products.

集输管道热水清蜡相变传热特性及影响因素

热洗清蜡是目前油田解决集输管道结蜡最常用的方法.掌握热洗清蜡过程的相变传热及清蜡时间的影响因素对于提高热洗清蜡效率至关重要.本文根据大庆原油中石蜡的成分组成,对结蜡层进行分层处理,利用焓法及VOF模型模拟了集输管道内石蜡的熔化过程.研究发现在自然对流作用下,管道上部石蜡熔化速率最快,左右两侧次之,下部石蜡熔化速率十分缓慢,是整个熔化过程的薄弱环节.石蜡完全熔化所需的时间随水温并非呈线性变化,随着水温的增加,其对缩短石蜡的熔化时间效果变弱.管内石蜡完全熔化所需时间与蜡层厚度成正比,但两者并不呈现线性增加关系,随蜡层厚度增大,石蜡完全熔化所需时间急剧增加.

Wheat straw-derived magnetic carbon foams: In-situ preparation and tunable high-performance microwave absorption

Recently,biomass-derived three-dimensional (3D) porous carbon materials have been gaining more interest as promising microwave absorbers due to their low cost,vast availability,and sustainability.Here,a novel 3D interconnected porous magnetic carbon foams are in-situ synthesized via a combination of sol-gel and carbonization process with wheat straw as the carbon source and FeCl3·6H2O as the magnetic regulating agent.During the process of foams formation,the lignocelluloses from the steam-exploded wheat straw are converted into interconnected carbon sheet networks with hierarchical porous structures,and the precursor FeCl3·6H2O is converted into magnetic nanoparticles uniformly embedded in the porous carbon foams.The generated magnetic nanoparticles are benefit to enhance the interface polarization and magnetic loss ability to improve the efficient complementarities between the dielectric and magnetic loss,thus increasing the impedance matching.The obtained sample treated at 600 ℃ displays the best microwave absorption (MA) performance.It presents a minimal reflection loss (RL) of-43.6 dB at 7.1 GHz and the effective bandwidth (RL <-10 dB) is 3.3 GHz with the thickness of 4.7 mm.The 3D porous structure,multi-interfaces and the synergy of dielectric loss and magnetic loss make great contribution to the outstanding MA performance.

Multiaxial electrospun generation of hollow graphene aerogel spheres for broadb and high-performance microwave absorption

Although graphene aerogels(GA)have been attracted great attention,the easy-operation and large-scale production of GA are still challenges.Further,most GA have a monolith-like appearance,limiting their application-specific needs.Herein,we highlight graphene aerogel spheres with controllable hollow structures(HGAS)that are delicately designed and manufactured via coaxial electrospinning coupled with freeze-drying and calcination.The HGAS exhibit a spherical configuration at the macroscale,while the construction elements of graphene on the microscale showing an interconnected radial microchannel structure.Further ball-in-ball graphene aerogel spheres(BGAS)are obtained by reference to the triaxial electrospinning technology.The as-prepared spheres possess the controllable integrated conductive networks,leading to the effective dielectric loss and impedance matching thus bringing on high-performance microwave absorption.The as-obtained HGAS shows a minimum reflection loss of-52.7 dB and a broad effective absorption bandwidth(f)of 7.0 GHz with thickness of 2.3 mm.Further,the fe reaches 9.3 GHz for BGAS with thickness of 3.4 mm.Aforementioned superior microwave absorption of HGAS and BGAS confirms combination of multiaxial electrospinning and freeze-drying on the multiscale is an effective strategy for scalable fabrication of advanced microwave.absorbing functional graphene aerogel spheres.

Generation of graphene-based aerogel microspheres for broadband and tunable high-performance microwave absorption by electrospinning-freeze drying process

Despite recent progress in the synthesis and application of graphene-based aerogels, some challenges such as scalable and cost-effective production, and miniaturization still remain, which hinder the practical application of these materials. Here we report a large-scale electrospinning method to generate graphene-based aerogel microspheres （AMs）, which show broadband, tunable and high-performance microwave absorption. Graphene/Fe3O4 AMs with a large number of openings with hierarchical connecting radial microcharmels can be obtained via electrospinning-freeze drying followed by calcination. Importantly, for a given Fe3O4：graphene mass ratio, altering the shape of aerogel monoliths or powders into aerogel microspheres leads to unique electromagnetic wave properties. As expected, the reflection loss of graphene/Fe3O4 AMs-1：1 with only 5 wt.% absorber loading reaches -51.5 dB at 9.2 GHz with a thickness of 4.0 mm and a broad absorption bandwidth （RL 〈-10 dB） of 6.5 GHz. Furthermore, switching to coaxial electrospinning enables the fabrication of SiO2 coatings to construct graphene/Fe3O4@SiO2 core-shell AMs. The coatings influence the electromagnetic wave absorption of graphene/Fe3O4 AMs significantly. In view of these advantages, we believe that this processing technique may be extended to fabricate a wide range of unique graphene-based architectures for functional design and applications.

Ultrathin flexible electrospun carbon nanofibers reinforced graphene microgasbags films with three-dimensional conductive network toward synergetic enhanced electromagnetic interference shielding

In recent years,graphene-based composite films have been greatly developed in the field of electromagnetic shielding interference(EMI).However,it is still a huge challenge to prepare graphene-based composite films with excellent mechanical properties,conductivity and electromagnetic shielding properties.In this work,we adopted a facile and effective method by annealing the alkali-treated polyacrylonitrile(aPAN)nanofibers reinforced graphene oxide(GO)composite films at 2000°C to obtain graphene-carbon nanofibers composite films(GCFs).Microscopically,carbon nanofibers(CNFs)were intercalated into the graphene sheets,and microgasbags structure was formed during the heat treatment process.The special structure makes GCFs have superior tensile strength(10.4 MPa)at 5%strain.After repeated folding over1000 times,the films still demonstrate excellent structural integrity and flexibility performance.Interestingly,the graphene-based composite films with 10 wt%a PAN nanofibers exhibit an extremely low density of about 0.678 g/cm^(3)and excellent electrical conductivity of 1.72×10^(5)S/m.Further,an outstanding electromagnetic shielding effectiveness(SE)of 55–57 d B was achieved,and the corresponding value of the specific SE/thickness can reach 67,601–70,059 d B·cm^(2)/g,which is the highest among reported graphenebased shielding materials.The significant electromagnetic shielding performance is due to the synergistic enhancement effect brought by the excellent conductivity of carbon nanofibers and graphene,the formed effective conductive network and the microgasbags structure.Electromagnetism simulation further clarified that the underlying mechanism should be mainly attributed to the conduction loss and multiple reflections caused by the special structure of GCFs.This work will provide new solutions for low density,high flexibility and excellent electromagnetic shielding properties materials in the next generation of foldable and wearable electronics.

Multifunctional aramid nanofibers reinforced RGO aerogels integrated with high-efciency microwave absorption, sound absorption and heat insulation performance

Although lightweight and three-dimensional(3 D) graphene aerogels are highly desirable for microwave absorption(MA) due to their high porosity,specific surface area,and 3 D conductive network,it still remains a large challenge to construct a multifunctional application framework to quickly adapt to the complex practical environment,making it to be efficiently applied in a variety of complex situation.Herein,multifunctional aramid nanofibers(ANFs) reinforced reduced graphene oxide aerogels(RGO@ANF) have been achieved by in-situ gel reaction,freeze-drying,and thermal annealing processes.The introduced ANFs in RGO aerogels can prevent the graphene sheets from over-stacking and enhance the connectivity of cell walls,thus leading to excellent compression resistance,MA,sound absorption,and thermal insulation performance.Under 70% strain,the maximum compressive stress of RGO@ANF aerogel reaches78.8 kPa,and reversible compressibility with reliable resistance to fatigue for 100 compressive cycles at20% strain.Further,the RGO@ANF aerogel exhibit a minimum reflection loss(RL_(min)) of-56.5 dB and a maximum effective absorption bandwidth(EAB) of 7.0 GHz at a thickness of 2.8 mm,basically covering the X and Ku bands.Moreover,the hybrid aerogel exhibited excellent sound absorption with an average absorption coefficient> 0.56 at 2-6 kHz and good thermal insulation performance with low thermal conductivity of about 49.18 mW m-1K-1.The integrated graphene aerogels with such multifunctional performances hold a great promise for applications such as MA,sound absorption,and heat insulation.

High-purity helical carbon nanotubes by trace-water- assisted chemical vapor deposition： Large-scale synthesis and growth mechanism

Helical carbon nanotubes （HCNTs） are highly desirable due to their unique geometrical elegance and inherent physical properties; however, high-efficiency synthesis of high-purity HCNTs with high yield and full elucidation of their growth mechanism remains challenging. Traditional methods to achieve the high-yield growth of HCNTs mainly focus on controlling the size of catalytic particles. Herein, we found that addition of trace water greatly benefits large-scale synthesis of HCNTs. Uniform HCNTs with - 100% purity can be obtained, and the yield of HCNTs can reach ~ 8,078% in a run of 6 h, much higher than that obtained without trace water and any of the reported yields. Experiments and theoretical simulations are performed to reveal that the trace water can react with the dangling bond on carbon, thus inhibiting the generation of amorphous species. Furthermore, the trace water can enhance the anisotropy of the catalyst surface. This results in different segregation rates of carbon atoms coming out of different crystal planes and further periodic mismatch of the graphite layers, thus leading to the formation of HCNTs. Therefore, this new and efficient method is promising for practical, large-scale production of HCNTs.