亲水型功能化石墨烯的分散性及其对水泥基复合材料力学性能的影响

为了解决石墨烯纳米片在水泥基体中的分散问题,采用芳基重氮盐(F)对氧化石墨烯(GO)进行改性,制备了一种新型亲水型功能化石墨烯(FG)。结果表明,FG在水溶剂中最大的分散浓度能够达到2.1 mg/mL。FTIR、拉曼光谱和XPS结果表明F成功对石墨烯进行了表面改性。对比纯水泥基体材料,本文所制备的亲水型FG/水泥复合材料的28天抗折强度和抗压强度相对提高了95.3%和78.3%。F对GO进行改性,实现了石墨烯在水泥基材料中的均匀分散及对其力学性能的提升。      

石墨烯/聚酰亚胺复合材料的制备与性能

以对苯二胺(PDA)和联苯四甲酸二酐(BPDA)为单体,合成了聚酰亚胺前驱体——聚酰胺酸溶液。采用溶液共混法将氧化石墨烯与聚酰胺酸复合,经制膜和热酰亚胺化反应制备了石墨烯/聚酰亚胺复合薄膜。用红外光谱(FT-IR)、拉曼光谱(Raman)、X射线衍射(XRD)和扫描电镜(SEM)对复合材料的结构和形态进行了分析。发现被还原的氧化石墨烯已经充分剥离并均匀分散在聚酰亚胺基体中,且与基体树脂结合紧密。力学性能测试表明,石墨烯的加入明显改善了聚酰亚胺的拉伸强度,当石墨烯含量为2%时,复合材料的拉伸强度提高了53%。热失重分析发现,复合薄膜的热稳定性也得到明显改善,相对于纯的聚酰亚胺,添加2%石墨烯的复合材料其热降解温度提高了10℃。     

改性氧化石墨烯相容剂的制备及在聚酰胺6/聚丙烯共混物中的应用研究

通过静电作用将氧化石墨烯(GO)与2,3-环氧丙基三甲基氯化铵(GTA)结合,得到GO-GTA,再与极性部分(HDE)和聚丙烯接枝马来酸酐(PP-g-MAH)反应制得相容剂PP-HDE-g-GO,将其加入聚酰胺6(PA6)/聚丙烯(PP)共混物中。通过扫描电子显微镜、X射线多晶衍射仪、热重和力学性能分析,研究了PP-HDE-g-GO含量对PA6/PP共混物性能的影响。结果表明:PP-HDE-g-GO改善了复合材料中两相的相容性,PP粒子均匀地分散于PA6基体;复合材料的热稳定性和力学性能均提高;当PP-HDE-g-GO添加量为0.2%(质量分数)时,复合材料综合性能最优。     

原位增容界面强度对PA6/PMMA共混物性能的影响

通过扫描电镜、差示扫描量热仪和力学性能测试等分析方法,研究甲基丙烯酸甲酯(MMA)和甲基丙烯酸缩水甘油酯(GMA)共聚物对尼龙6(PA6)/PMMA共混物形态结构、结晶行为和力学性能的影响。结果表明,P(MMA-co-GMA)可以提高PA6与PMMA的相容性,改善共混物的拉伸性能,但其增容效果取决于P(MMA-co-GMA)中的环氧基团与PA6末端氨基所形成的接枝共聚物的数量,只有当其达到某一临界值时,共混物才具有最佳的力学性能,并且加入P(MMA-co-GMA)后,基体相PA6的结晶能力降低,导致共混物在拉伸过程中出现二次屈服行为。     

尼龙6/半芳香族尼龙阻隔薄膜的制备及特性EI北大核心CSCD

通过尼龙6(PA6)和半芳香族尼龙(MXD6)熔融共混的简单方法制备了一系列的PA6/MXD6共混物,以提高PA6薄膜的阻隔性能。将PA6/MXD6吹塑成膜,利用差示扫描量热法(DSC)、X射线衍射(XRD)、雾度测试和渗透率测试等手段研究了MXD6加入量对薄膜各种性能的影响。此外,考虑到PA6薄膜在耐蒸煮包装领域的应用,文中同时探讨了高温蒸煮对PA6/MXD6共混物薄膜微观结晶结构的影响。PA6/MXD6薄膜的氧气渗透系数会随MXD6的加入而显著降低,明显提高了薄膜的阻隔性,当MXD6用量为20%时达到最佳值;MXD6的加入还显著提高了PA6薄膜的透明性,雾度测试发现PA6/MXD6共混物薄膜的雾度随着MXD6的含量增加而减小,MXD6含量为50%时,其雾度仅为3.59%;DSC和XRD测试结果发现,高温蒸煮过程会提高PA6/MXD6薄膜的结晶度,并促使γ晶型向α晶型转变。熔融共混法利于PA6/MXD6薄膜的大规模生产。     

废弃LDPE / PA6 / LLDPE 复合膜回收再生的研究

以废弃缓冲空气垫( LDPE/ PA6/ LLDPE) 复合薄膜为基体材料,低密度聚乙烯接枝马来酸酐( LDPE-g-MAH)为相容剂,通过混合、挤出、吹塑工艺制备了LDPE/ PA6/ LLDPE 再生共混材料,并对相容剂添加量(质量分数)分别为3%,8%,12%,16%时再生共混材料的力学性能、阻隔性能、熔体流动性能和微观形态结构进行了测试与分析。结果表明,LDPE-g-MAH 的加入明显改善了尼龙和聚乙烯共混两相的界面相容性;相容剂添加量为3% ~8%的再生共混材料的阻隔性能较好,相容剂添加量为8% ~16% 的共混合金的力学性能得到了显著提高。     

尼龙6/半芳香族尼龙阻隔薄膜的制备及特性

通过尼龙6(PA6)和半芳香族尼龙(MXD6)熔融共混的简单方法制备了一系列的PA6/MXD6共混物,以提高PA6薄膜的阻隔性能。将PA6/MXD6吹塑成膜,利用差示扫描量热法(DSC)、X射线衍射(XRD)、雾度测试和渗透率测试等手段研究了MXD6加入量对薄膜各种性能的影响。此外,考虑到PA6薄膜在耐蒸煮包装领域的应用,文中同时探讨了高温蒸煮对PA6/MXD6共混物薄膜微观结晶结构的影响。PA6/MXD6薄膜的氧气渗透系数会随MXD6的加入而显著降低,明显提高了薄膜的阻隔性,当MXD6用量为20%时达到最佳值;MXD6的加入还显著提高了PA6薄膜的透明性,雾度测试发现PA6/MXD6共混物薄膜的雾度随着MXD6的含量增加而减小,MXD6含量为50%时,其雾度仅为3.59%;DSC和XRD测试结果发现,高温蒸煮过程会提高PA6/MXD6薄膜的结晶度,并促使γ晶型向α晶型转变。熔融共混法利于PA6/MXD6薄膜的大规模生产。     

石墨烯/聚酰胺6纤维的混合熔融纺丝工艺及性能EI北大核心CSCD

采用溶液混合冷冻干燥法制备了质量分数0.004%的石墨烯/聚酰胺6(PA6)粒料,再用2种工艺制备石墨烯/PA6纤维——石墨烯/PA6粒料直接熔融纺丝;石墨烯/PA6粒料加入双螺杆挤出机熔融混合、挤出、造粒、熔融纺丝。用万能试验机测试了纤维的拉伸性能;用差示扫描量热分析测试了纤维的熔融行为并计算了结晶度;用扫描电镜(SEM)观察了石墨烯/PA6纤维的微观形态。研究结果表明,微量石墨烯的加入能够显著改善PA6纤维的拉伸性能,制备的石墨烯/PA6纤维的拉伸强度和拉伸模量分别可达到270 MPa和9.4GPa;工艺一制备的石墨烯/PA6纤维的热力学性能优于工艺二;较高的熔融纺丝温度可提高纤维的拉伸强度、拉伸模量、熔点和结晶度;SEM分析表明,石墨烯较均匀地分散在PA6基体中,纤维表面均匀,无明显瑕疵。     

多壁碳纳米管/氧化石墨烯/硅橡胶复合薄膜湿敏性能研究

采用化学修饰的多壁碳纳米管(o-MWCNTs)与Hummers法制备的氧化石墨烯(GO)超声混合,加入室温硫化硅橡胶(RTV),利用溶液共混法制备具有湿敏特性的o-MWCNTs/GO/RTV复合薄膜。借助于透射电子显微镜(TEM)、红外吸收光谱(FT-IR)等分析手段分别对化学修饰的多壁碳纳米管及氧化石墨烯进行表征,并对基于o-MWCNTs/GO/RTV的复合薄膜的湿敏性能及湿敏机理进行了探讨。结果表明,混酸处理后的碳纳米管端口打开,侧壁和开端处产生羧基和羟基等官能团,有利于水分子的吸附,同时也有利于与GO表面的基团作用,形成三维的纳微米结构,提高了碳纳米管与硅橡胶基体的相容性,使所制备的o-MWCNTs/GO/RTV复合薄膜灵敏度提高。当相对湿度在23%~87%的范围,m(GO)∶m(o-MWCNTs)=1∶3时,o-MWCNTs/GO/RTV复合薄膜的湿滞为5%RH,灵敏度为0.3152/%RH,响应时间和恢复时间分别为4和27 s。     

石墨烯/聚酰胺6纤维的混合熔融纺丝工艺及性能

采用溶液混合冷冻干燥法制备了质量分数0.004%的石墨烯/聚酰胺6(PA6)粒料,再用2种工艺制备石墨烯/PA6纤维——石墨烯/PA6粒料直接熔融纺丝;石墨烯/PA6粒料加入双螺杆挤出机熔融混合、挤出、造粒、熔融纺丝。用万能试验机测试了纤维的拉伸性能;用差示扫描量热分析测试了纤维的熔融行为并计算了结晶度;用扫描电镜(SEM)观察了石墨烯/PA6纤维的微观形态。研究结果表明,微量石墨烯的加入能够显著改善PA6纤维的拉伸性能,制备的石墨烯/PA6纤维的拉伸强度和拉伸模量分别可达到270 MPa和9.4GPa;工艺一制备的石墨烯/PA6纤维的热力学性能优于工艺二;较高的熔融纺丝温度可提高纤维的拉伸强度、拉伸模量、熔点和结晶度;SEM分析表明,石墨烯较均匀地分散在PA6基体中,纤维表面均匀,无明显瑕疵。     

One‐Step Formation of a Single Atomic‐Layer Transistor by the Selective Fluorination of a Graphene Film

In this study, the scalable and one‐step fabrication of single atomic‐layer transistors is demonstrated by the selective fluorination of graphene using a low‐damage CF₄ plasma treatment, where the generated F‐radicals preferentially fluorinated the graphene at low temperature (<200 °C) while defect formation was suppressed by screening out the effect of ion damage. The chemical structure of the C–F bonds is well correlated with their optical and electrical properties in fluorinated graphene, as determined by X‐ray photoelectron spectroscopy, Raman spectroscopy, and optical and electrical characterizations. The electrical conductivity of the resultant fluorinated graphene (F‐graphene) was demonstrated to be in the range between 1.6 kΩ/sq and 1 MΩ/sq by adjusting the stoichiometric ratio of C/F in the range between 27.4 and 5.6, respectively. Moreover, a unique heterojunction structure of semi‐metal/semiconductor/insulator can be directly formed in a single layer of graphene using a one‐step fluorination process by introducing a Au thin‐film as a buffer layer. With this heterojunction structure, it would be possible to fabricate transistors in a single graphene film via a one‐step fluorination process, in which pristine graphene, partial F‐graphene, and highly F‐graphene serve as the source/drain contacts, the channel, and the channel isolation in a transistor, respectively. The demonstrated graphene transistor exhibits an on‐off ratio above 10, which is 3‐fold higher than that of devices made from pristine graphene. This efficient transistor fabrication method produces electrical heterojunctions of graphene over a large area and with selective patterning, providing the potential for the integration of electronics down to the single atomic‐layer scale.     

Isotope Engineered Fluorinated Single and Bilayer Graphene: Insights into Fluorination Selectivity,Stability, and Defect Passivation

Tailoring the physicochemical properties of graphene through functionalization remains a major interest for next-generation technological applications. However, defect formation due to functionalization greatly endangers the intrinsic properties of graphene, which remains a serious concern. Despite numerous attempts to address this issue, a comprehensive analysis has not been conducted. This work reports a two-step fluorination process to stabilize the fluorinated graphene and obtain control over the fluorination-induced defects in graphene layers. The structural, electronic and isotope-mass-sensitive spectroscopic characterization unveils several not-yet-resolved facts, such as fluorination sites and C F bond stability in partially-fluorinated graphene (F-SLG). The stability of fluorine has been correlated to fluorine co-shared between two graphene layers in fluorinated-bilayer-graphene (F-BLG). The desorption energy of co-shared fluorine is an order of magnitude higher than the C F bond energy in F-SLG due to the electrostatic interaction and the inhibition of defluorination in the F-BLG. Additionally, F-BLG exhibits enhanced light–matter interaction, which has been utilized to design a proof-of-concept field-effect phototransistor that produces high photocurrent response at a time <200 µs. Thus, the study paves a new avenue for the in-depth understanding and practical utilization of fluorinated graphenic carbon.     

The characteristics of fluorinated polycrystalline silicon oxides and thin film transistors by CF4 plasma treatment

This study describes a simple fluorinating technique by the tetrafluoromethane (CF₄) plasma treatment to form fluorinated polyoxides and polycrystalline silicon thin film transistors (TFTs). In comparison with the non-fluorinated device, the fluorinated polyoxides and devices exhibit a higher breakdown field (>8 MV/cm), low charge trapping rates, low off-state current, and low trap states. Furthermore, the performance and reliability of the fluorinated devices are also improved by the CF₄ plasma treatment. This is due to the fact that the incorporated fluorine can break strain bonds to form stronger silicon-fluorine (Si-F) bonds to passivate the generation of interface and trap states existing near the polyoxide/polysilicon interface and grain boundaries.     

Nylon-6/Graphene composites modified through polymeric modification of graphene

The covalent functionalization of graphene oxide (GO) with poly(vinyl alcohol) (PVA) via ester linkages (GO-es-PVA) as well as the characterization of modified graphene based Nylon-6 (PA6) composite prepared by solution mixing techniques was examined. The anchoring of PVA chains on GO sheets was confirmed by XPS and FTIR measurements. The resulting functionalized sample became soluble in formic acid, allowing solution-phase processing for preparation of PA6/GO composites. Answering to the efficient polymer-chain grafting, a homogeneously dispersion of GO sheets in PA6 matrix and a dramatic improvement of interface adhesion between nanosheets and matrix were observed in PA6/GO-es-PVA composites by SEM and TEM. The depressed crystallization of PA6 chains in PA6/GO-es-PVA composites was investigated by their DSC and XRD results.     

Highly controllable and green reduction of graphene oxide to flexible graphene film with high strength

Graphene film with high strength was fabricated by the assembly of graphene sheets derived from graphene oxide (GO) in an effective and environmentally friendly approach. Highly controllable reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant, in which the reduction process was monitored by XRD analysis and UV–vis absorption spectra. Self-assembly of the as-made CCG sheets results in a flexible CCG film. This method may open an avenue to the easy and scalable preparation of graphene film with high strength which has promising potentials in many fields where strong, flexible and electrically conductive films are highly demanded.     

Formation and field emission of patterned zinc oxide-adhering graphene cathodes

Large scale zinc oxide (ZnO)-adhering patterned graphene cathodes were realized by using spin-coating technique, and their field emission characteristics were investigated. The graphene sheets edges are extracted from the hybrid cathode to form emission centers, leading to high field enhancement and low threshold field. The ZnO film improves the interface contact and adhesion of graphene sheets with the electrode and acts as negative feedback resistive layer, which contributes to the uniformity and long-time stability. Our study opens up avenues for application of graphene sheets in field emission device utilizing efficient, large scale, pattern and low-cost technology.     

Enhanced thermal-conductive and anti-dripping properties of polyamide composites by 3D graphene structures at low filler content

In this work, 3D graphene structures constructed by graphene foam (GF) were introduced into polyamide-6 (PA6) matrix for the purpose of enhancing the thermal-conductive and anti-dripping properties of PA6 composites. The GF were prepared by one-step hydrothermal method. The PA6 composites were synthesized by in-situ thermal polycondensation method to realize PA6 chains covalently grafted onto the graphene sheets. The 3D interconnected graphene structure favored the formation of the consecutive thermal conductive paths or networks even at relatively low graphene loadings. As a result, the thermal conductivity was improved by 300% to 0.847 W·m⁻¹·K⁻¹ of PA6 composites at 2.0 wt% graphene loading from 0.210 W·m⁻¹·K⁻¹ of pure PA6 matrix. The presence of self-supported 3D structure alone with the covalently-grafted PA6 chains endowed the PA6 composites good anti-dripping properties.     

Electrodeposition of graphene layers doped with Brϕnsted acids

A simple and fast method is demonstrated for the preparation of a thin film of graphene layers by the electrodeposition of positively doped graphene dispersion onto desired electrode substrates. A thin film of graphene layers was obtained by applying negative potentials according to the electrophoretic deposition mechanism. The doped graphene dispersion was prepared from expanded graphite treatment with various acids (HCl, HNO₃, and H₂SO₄) and an ultrasonication process. The doping and deposition processes are strongly dependent on the type of acid and the applied potential, which were monitored by Raman spectroscopy and quartz crystal microbalance, respectively. The morphology and electrochemical properties of the graphene film were characterized by scanning electron microscopy and cyclic voltammetry. The electrochemical performance of graphene film obtained using nitric acid or hydrochloric acid dopant is superior to that obtained with sulfuric acid doping. This technique could be a facile tool for the fabrication of a thin film of graphene layers on a desired substrate.     

The safer and scalable mechanochemical synthesis of edge-chlorinated and fluorinated few-layer graphenes

Halogen functionalization of the edges of the graphene sheets can improve processability, add new properties, and enhance its interactions with other materials. Through functionalization, improved materials can be realized. Typically, halogenated graphenes are produced from pure or reactive halogen sources. Current approaches present significant safety challenges. By generating reactive dichlorine monoxide (Cl₂O) in situ, a chlorinated graphene with the nominal composition C₁₇Cl₂OH can be realized safely and scalably. Chlorinated graphene can be used as a precursor for an array of functionalized materials by mechanically driven solid-state metathesis reactions. For example, nearly 75% of the chlorine in chlorinated graphene can be exchanged with fluorine by using the safer fluorine-containing compound ammonium fluoride (NH₄F) as a reagent. A material with the composition C₃₄Cl₃F(OH)₂ is realized. Preliminary work shows that F–graphene has oxygen reduction properties and Cl–graphene can improve existing zinc–air fuel cells. A scalable production of chlorinated and fluorinated graphenes and graphites will accelerate their adoption in fuel cells, batteries, polymer composites, and catalysts.     

Preparation and characterization of long-chain alkyl silane-functionalized graphene film

Functionalized graphene (FG) was prepared in one step by treating graphene oxide (GO) successively with hexadecyltrimethoxysilane and triethylamine. The FG sheets were subsequently assembled into a thin film by vacuum extraction filtering. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, X-ray diffraction, and Raman spectroscopy were employed to confirm the reduction and silane functionalization of GO to be simultaneously completed during the treatment. The presence of the long hexadecyl chain made the FG hydrophobic. The graphene film showed a high surface roughness, which consisted of many randomly stacked flakes, exhibiting a contact angle of up to 128.1°.