钢表面激光熔覆钴基合金层的组织和耐磨性的研究

采用CO₂横流激光在40Cr钢表面熔覆不同配比的钴基合金粉末,采用摩擦磨损试验机测试试样的摩擦磨损性能。对摩擦系数以及耐磨性均较高的试样,采用微观分析及力学性能测试手段对熔覆层显微组织、物相、成分进行比较研究。结果表明:在现有实验条件下,激光熔覆层的强化相呈现网络状加弥散分布的颗粒状使裂纹或者缺陷的萌生门槛值增加,裂纹扩展速率减慢,导致钴基合金激光熔覆层的摩擦系数和耐磨性能的协同提高。     

不锈钢表面镍铬激光熔敷层组织与耐磨性能的研究

研究了不锈钢表面镍铬激光熔敷层的组织与耐磨性能。结果表明，熔敷层组织细小均匀，有硬化相存在，并具有良好的耐磨性能。     

石墨烯/NiAu复合透明导电层在GaN LED的应用

通过溅射方法制备Ni/Au层,用作石墨烯和p型GaN之间的插入层来减小接触电势。研究了Ni和Au的厚度比与GaN LED性能的关系。结果表明,在1.5 nm总厚度的条件下,Ni与Au厚度比为1 nm/0.5 nm时为最佳,可同时兼顾透光性能和良好欧姆接触,此时,石墨烯/NiAu复合透明导电层可以明显地降低GaN LED的工作电压,同时在蓝光波段具有很高的透光率,因而提高了GaN LED的发光性能。     

30CrMnSiA钢激光表面淬火的显微组织及耐磨性

采用功率为 2kW ,扫描速度为 10 0mm/min的工艺参数对钻杆接头材料 30CrMnSiA钢进行了表面相变硬化处理 ,研究了相变层的组织和耐磨性。实验结果表明 ,30CrMnSiA钢表面相变硬化层分为完全淬硬层、过度层和受热影响的基体组织 ,硬化层的显微组织明显细化 ,其表面层的耐磨性明显高于未经激光处理的 30CrMnSiA钢。     

微球体尺度对硅片表面改性效果的影响

以单晶硅(110)和C 注入硅片后形成的表面改性层为研究对象,对C 注入单晶硅后的离子分布深度概率进行模拟计算,选择不同直径尺度的SiO2球与其配副,在UMT-Ⅱ微摩擦磨损试验机上开展微载荷和不同球径尺度下的摩擦磨损试验,分析C 注入前后硅片的摩擦系数变化规律,在MicroXAMTM超高精度三维轮廓仪和S-3000N型扫描电镜上观察硅片磨损后的微观形貌.结果表明,C 注入对单晶硅表面的摩擦磨损性能改善明显,改善效果与施加的微载荷和接触应力相关.载荷小于0.1 N时,C 注入后硅片的减摩效果不明显;载荷大于0.2 N时,C 注入后硅片的耐磨性显著提高,其磨损机理主要为磨粒磨损和粘着磨损.     

铸铁表面抗裂耐磨激光熔敷材料的研制

采用铁基熔敷材料 ,在不预热情况下通过调整熔敷金属Ni含量 ,改变铸铁激光熔敷层内奥氏体相与渗碳体相体积分数 ,进而抑制熔敷层裂纹的产生。在抗裂性最佳激光熔敷工艺参数基础上 ,研究了Ni对熔敷层奥氏体体积分数及表面裂纹率的影响 ,揭示了熔敷层开裂的微观机制 ,获得了搭接 2 5道熔敷层不裂的Fe C Si Ni系熔敷材料。以此熔敷材料为基础 ,改变钛粉含量 ,在熔敷层得到原位自生TiC ,研究了TiC对熔敷层耐磨性的影响 ,分析了TiC数量对熔敷层磨损形貌及磨损质量损失的影响规律 ,最终获得了可显著提高熔敷层抗裂性及耐磨性的Fe C Si Ni Ti熔敷材料。     

Layer‐by‐Layer Assembly of 3D Tissue Constructs with Functionalized Graphene

Carbon‐based nanomaterials have been considered promising candidates to mimic certain structure and function of native extracellular matrix materials for tissue engineering. Significant progress has been made in fabricating carbon nanoparticle‐incorporated cell culture substrates, but only a limited number of studies have been reported on the development of 3D tissue constructs using these nanomaterials. Here, a novel approach to engineer 3D multilayer constructs using layer‐by‐layer (LbL) assembly of cells separated with self‐assembled graphene oxide (GO)‐based thin films is presented. The GO‐based structures are shown to serve as cell adhesive sheets that effectively facilitate the formation of multilayer cell constructs with interlayer connectivity. By controlling the amount of GO deposited in forming the thin films, the thickness of the multilayer tissue constructs could be tuned with high cell viability. Specifically, this approach could be useful for creating dense and tightly connected cardiac tissues through the co‐culture of cardiomyocytes and other cell types. In this work, the fabrication of stand‐alone multilayer cardiac tissues with strong spontaneous beating behavior and programmable pumping properties is demonstrated. Therefore, this LbL‐based cell construct fabrication approach, utilizing GO thin films formed directly on cell surfaces, has great potential in engineering 3D tissue structures with improved organization, electrophysiological function, and mechanical integrity.     

负极性电火花加工时的电极损耗机理及积碳层的减损作用研究

本文基于场致发射理论,对负极性电火花加工时电极材料的损耗情况及极间做功能量进行了研究,设计并分别进行了不同工艺参数下紫铜电极和A3#钢电极单孔负极性电火花加工对比实验.实验研究结果表明:相同工艺参数下,紫铜电极比A3#钢电极加工时的极间放电能量大,加工效率高且电极材料的损耗率低:表面积碳层对紫铜电极材料有着良好的减损作用,而对A3#钢电极则作用甚微;且对紫铜电极而言,在保证有效消电离的情况下,极间有效放电时间比越高,加工效率越高,电极的损耗率越低,而相应的积碳层对电极材料的减损率则减小.     

Regulating Cellular Behavior on Few‐Layer Reduced Graphene Oxide Films with Well‐Controlled Reduction States

Understanding the effect of graphene on cellular behavior is important for enabling a range of new biological and biomedical applications. However, due to the complexity of cell responses and graphene surface states, regulating cellular behaviors on graphene or its derivatives is still a great challenge. To address this challenge we have developed a novel, facile route to regulate the cellular behaviors on few‐layer reduced graphene oxide (FRGO) films by controlling the reduction states of graphene oxide. Our results indicate that the surface oxygen content of FRGO has a strong influence on cellular behavior, with the best performance for cell attachment, proliferation and phenotype being obtained in moderately reduced FRGO. Cell performance decreased significantly as the FRGO was highly reduced. Moderate performance was found in non‐reduced pure graphene oxide and control glass slides. Our results highlight the important role of surface physicochemical characteristics of graphene and its derivatives in their interactions with biocomponents, and may have great potential in enabling the utility of graphene based materials in various biomedical and bioelectronic applications.     

Stiff and Transparent Multilayer Thin Films Prepared Through Hydrogen‐Bonding Layer‐by‐Layer Assembly of Graphene and Polymer

Due to their exceptional orientation of 2D nanofillers, layer‐by‐layer (LbL) assembled polymer/graphene oxide thin films exhibit unmatched mechanical performance relative to any conventionally produced counterparts with similar composition. Unprecedented mechanical property improvement, by replacing graphene oxide with pristine graphene, is demonstrated in this work. Polyvinylpyrrolidone‐stabilized graphene platelets are alternately deposited with poly(acrylic acid) using hydrogen bonding assisted LbL assembly. Transmission electron microscopy imaging and the Halpin‐Tsai model are used to demonstrate, for the first time, that intact graphene can be processed from water to generate polymer nanocomposite thin films with simultaneous parallel‐alignment, high packing density, and exfoliation. A multilayer thin film with only 3.9 vol% of highly exfoliated, and structurally intact graphene, increases the elastic modulus (E) of a polymer multilayer thin film by 322% (from 1.41 to 4.81 GPa), while maintaining visible light transmittance of ≈90%. This is one of the greatest improvements in elastic modulus ever reported for a graphene‐filled polymer nanocomposite with a glassy (E > 1 GPa) matrix. The technique described here provides a powerful new tool to improve nanocomposite properties (mechanical, gas transport, etc.) that can be universally applied to a variety of polymer matrices and 2D nanoplatelets.     

石墨烯上生长GaN纳米线的研究

在常压条件下采用化学气相淀积(CVD)技术在有石墨烯插入层的衬底上生长GaN纳米线,研究了生长温度、石墨烯插入层、催化剂等因素对GaN纳米线的形貌、光学特性以及结构的影响.通过扫描电子显微镜(SEM)、光致发光(PL)谱、拉曼(Raman)谱和透射电子显微镜(TEM)等表征手段对GaN纳米线的形貌、光学特性以及结构进行表征.结果表明,在1 100℃条件下,同时有石墨烯插层和催化剂的衬底表面能够获得低应力单晶GaN纳米线.石墨烯、催化剂对于获得低应力单晶GaN纳米线有重要的作用.     

Boosting the Electrical Double‐Layer Capacitance of Graphene by Self‐Doped Defects through Ball‐Milling

Improving the capacitance of carbon materials for supercapacitors without sacrificing their rate performance, especially volumetric capacitance at high mass loadings, is a big challenge because of the limited assessable surface area and sluggish electrochemical kinetics of the pseudocapacitive reactions. Here, it is demonstrated that “self‐doping” defects in carbon materials can contribute to additional capacitance with an electrical double‐layer behavior, thus promoting a significant increase in the specific capacitance. As an exemplification, a novel defect‐enriched graphene block with a low specific surface area of 29.7 m² g^?1 and high packing density of 0.917 g cm^?3 performs high gravimetric, volumetric, and areal capacitances of 235 F g^?1, 215 F cm^?3, and 3.95 F cm^?2 (mass loading of 22 mg cm^?2) at 1 A g^?1, respectively, as well as outstanding rate performance. The resulting specific areal capacitance reaches an ultrahigh value of 7.91 F m^?2 including a “self‐doping” defect contribution of 4.81 F m^?2, which is dramatically higher than the theoretical capacitance of graphene (0.21 F m^?2) and most of the reported carbon‐based materials. Therefore, the defect engineering route broadens the avenue to further improve the capacitive performance of carbon materials, especially for compact energy storage under limited surface areas.     

In Situ Production of Biofunctionalized Few‐Layer Defect‐Free Microsheets of Graphene

Biological interfacing of graphene has become crucial to improve its biocompatibility, dispersability, and selectivity. However, biofunctionalization of graphene without yielding defects in its sp²‐carbon lattice is a major challenge. Here, a process is set out for biofunctionalized defect‐free graphene synthesis through the liquid phase ultrasonic exfoliation of raw graphitic material assisted by the self‐assembling fungal hydrophobin Vmh2. This protein (extracted from the edible fungus Pleurotus ostreatus) is endowed with peculiar physicochemical properties, exceptional stability, and versatility. The unique properties of Vmh2 and, above all, its superior hydrophobicity, and stability allow to obtain a highly concentrated (≈440–510 μg mL^?1) and stable exfoliated material (ζ‐potential, +40/+70 mV). In addition controlled centrifugation enables the selection of biofunctionalized few‐layer defect‐free micrographene flakes, as assessed by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and electrophoretic mobility. This biofunctionalized product represents a high value added material for the emerging applications of graphene in the biotechnological field such as sensing, nanomedicine, and bioelectronics technologies.     

石墨烯上生长GaN纳米线

采用金属Ga升华法在石墨烯/蓝宝石衬底上生长了高质量GaN纳米线,研究了不同的生长条件,如NH3流量、反应时间、催化剂和缓冲层等对GaN纳米线形貌的影响,采用扫描电子显微镜(SEM)对GaN纳米线进行表征.研究发现,在适当的NH3流量且无催化剂时,衬底上可以生长出粗细均匀的GaN纳米线.反应时间为5 min时,纳米线密集分布在衬底上,表面光滑.在石墨烯/蓝宝石上预先低温生长GaN缓冲层,然后升温至1 100℃进行GaN纳米线生长,获得了具有择优取向的GaN纳米线结构.研究表明,石墨烯和缓冲层对获得GaN纳米线结构有序阵列具有重要的作用.     

液晶玻盒结构中PI层摩擦定向的实现

液晶玻璃表面涂敷一层有机高分子薄膜,这层薄膜是液晶玻盒结构的一个重要组成部分,行业内称之为液晶玻盒定向层（PI层）。这层薄膜经过绒布类材料高速摩擦来实现定向,使玻盒内的液晶分子可以按照摩擦所产生的沟槽方向来实现想要达到的均匀有序排列。文章主要介绍了摩擦工艺实现的方法以及摩擦胶辊与摩擦布的设计与选用。     

激光熔覆层摩擦学特性的研究

为研究激光熔覆层的磨损性能，采用激光熔覆技术，在球墨铸铁材料表面制备原位析出颗粒增强金属基复合材料表层。以激光强化的球墨铸铁为上试样、灰铸铁为下试样，进行标准的SRV快速磨损试验。利用表面形貌仪测量配副双方的磨损深度，扫描电子显微镜（SEM）观察磨痕形貌。结果表明；激光熔覆强化层与灰铸铁配副，磨损深度分别为1．78μm、0．87μm，摩擦系数在0．067～0．085内变化，摩擦系数随摩擦时间的增加呈逐渐降低的趋势；磨损机制为微切削。     

Superplastic Air‐Dryable Graphene Hydrogels for Wet‐Press Assembly of Ultrastrong Superelastic Aerogels with Infinite Macroscale

Highly compressible graphene‐based monoliths with excellent mechanical, electrical, and thermal properties hold great potential as multifunctional structural materials to realize the targets of energy‐efficiency, comfort, and safety for buildings, vehicles, aircrafts, etc. Unfortunately, the ultralow mechanical strength and limited macroscale have hampered their practical applications. Herein, ultrastrong superelastic graphene aerogel with infinite macroscale is obtained by a facile wet‐press assembly strategy based on the novel superplastic air‐dryable graphene hydrogel (SAGH). The SAGH with isotropic, open‐cell, and highly porous microstructure is carefully designed by a dual‐template sol–gel method. Countless SAGH “bricks” can be assembled together orderly by press to form the strongly combined wet‐press assembled graphene aerogel (WAGA) “wall” after air‐drying. The WAGA with highly oriented, dense, multiple‐arch microstructure possesses arbitrary macroscale, outstanding compressive strength (47 MPa, over 10 times higher than the best ever reported), super elasticity (>97% strain), and high conductivity (378 S m^?1). The strong adhesion is attributed to the tightly face‐to‐face contacted graphene interfaces caused by wet‐press and air‐drying. The WAGAs prove to be excellent multifunctional structural materials in the fields of high pressure/strain sensor, tunable mechanical energy absorber, high‐performance fire‐resistance, and thermal insulation. This facile strategy is easily extended to fabricate other similar metamaterials.     

Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants

Doping of graphene is a viable route toward enhancing its electrical conductivity and modulating its work function for a wide range of technological applications. In this work, the authors demonstrate facile, solution‐based, noncovalent surface doping of few‐layer graphene (FLG) using a series of molecular metal‐organic and organic species of varying n‐ and p‐type doping strengths. In doing so, the authors tune the electronic, optical, and transport properties of FLG. The authors modulate the work function of graphene over a range of 2.4 eV (from 2.9 to 5.3 eV)—unprecedented for solution‐based doping—via surface electron transfer. A substantial improvement of the conductivity of FLG is attributed to increasing carrier density, slightly offset by a minor reduction of mobility via Coulomb scattering. The mobility of single layer graphene has been reported to decrease significantly more via similar surface doping than FLG, which has the ability to screen buried layers. The dopant dosage influences the properties of FLG and reveals an optimal window of dopant coverage for the best transport properties, wherein dopant molecules aggregate into small and isolated clusters on the surface of FLG. This study shows how soluble molecular dopants can easily and effectively tune the work function and improve the optoelectronic properties of graphene.     

Maintaining Cytocompatibility of Biopolymers Through a Graphene Layer for Electrical Stimulation of Nerve Cells

Here, the utility of large‐area graphene as a flexible, biocompatible electrode to stimulate cell growth is demonstrated. Chemical vapor deposition allows the production of highly crystalline, single, double, or few‐layered graphene on copper substrates. The subsequent transfer to a biopolymer support, such as polylactic acid (PLA) or polylactic‐co‐glycolic acid (PLGA) copolymers, provides a unique electrode structure retaining the flexibility and surface properties of the underlying materials with a conductive graphene layer sufficient to enable electrical communication with excitable cells. The growth and compatibility of PC‐12 cells on these graphene‐biopolymer (GPB) electrodes is influenced more by the underlying polymer than the presence of graphene, demonstrating that the characteristics influencing biocompatibility have been retained after graphene modification. Differentiation of these cells into neural phenotypes is enhanced using electrical stimulation through the graphene conductive layer, confirming that the conductivity of graphene is sufficient to electrically communicate with cells grown on the surface. The process described herein demonstrates that non‐conducting, flexible biopolymer surfaces can be easily coated with graphene without changing the biocompatibility of the materials. This could be used to create electrodes from non‐conducting materials with optimized cell compatibility with graphene providing electrical properties suitable for stimulation of cells without greatly changing the surface properties.