双相不锈钢焊接接头的耐蚀性介绍

综述了双相不锈铜的焊接接头的耐蚀性研究进展,及采用的研究方法和已取得的成果。主要介绍了异种金属焊接接头的组织及其对双相不锈铜的耐蚀性能的影响.此外,还叙述了在焊接过程中,不同的热处理方式,不同的焊接工艺对双相不锈钢焊接接头的应力腐蚀、晶间腐蚀和点蚀的影响：结果表明：采用合适的输入热能量,进行多层焊接,选用Ar＋2％N2作为混合保护气,采用手工电弧焊（SMAW）和钨极氩弧焊（TIG）相配合的方法,可以使得焊接接头具有优良的耐蚀性能。     

磷酸功能化有机无机SiO2复合防腐涂层的结构及性能研究

采用溶胶-凝胶法,以γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)与正硅酸乙酯(TEOS)进行水解聚合,再与磷酸氢二(甲基丙烯酰氧乙基)酯(EGMP)进行自由基聚合,在马口铁上制备有机无机复合防腐涂层。通过傅里叶变换红外光谱表征涂层结构,扫描电镜研究涂层的微观表面,附着力测试研究涂层对基材的附着水平,极化曲线以及中性盐雾测试对复合薄膜的防腐性能测试,并探讨了EGMP量对涂层的性能的影响。结果表明,有机无机网络结构已形成,表面致密光滑,其附着力水平达到1级,n(KH570)∶n(EGMP)=4∶1时涂层的防腐性能最好。     

PVA/Carbon Dot Nanocomposite Hydrogels for Simple Introduction of Ag Nanoparticles with Enhanced Antibacterial Activity

The introduction of nanomaterials to hydrogels is an effective way to improve the mechanical properties of hydrogels. Herein, carbon nanodot (C‐dot) as a new‐found excellent nanomaterial is first added to polyvinyl alcohol (PVA) hydrogel to prepare PVA/C‐dot hydrogel by freeze–thaw method. The appropriate size and plenty of surface functional groups make C‐dot an ideal nucleating agent for PVA crystallization, which leads to form a denser and more uniform cross‐linked network in PVA hydrogel, and in turn enhance the mechanical properties of PVA hydrogel. Compared to pure PVA hydrogel, about a 46.4% increase of tensile strength and 18.5% increase of elongation at break are achieved when the content of C‐dot in PVA/C‐dot hydrogel is 2 wt%, suggesting that C‐dot can effectively improve the mechanical properties of PVA hydrogel. Besides, C‐dot can endow PVA hydrogel with some new properties, such as fluorescence and reducibility. Herein, Ag nanoparticles are simply introduced and uniformly dispersed in PVA hydrogels with the help of reducibility of C‐dot, which can greatly enhance the antibacterial activity of PVA/C‐dot hydrogels, and enlarge their application potential in medical field.

     

Influence of processing conditions in small‐scale melt mixing and compression molding on the resistivity and morphology of polycarbonate–MWNT composites

Polycarbonate (PC) composites containing 1 wt % multiwalled carbon nanotubes (MWNT) were produced in a small‐scale DACA microcompounder under variation of mixing temperature and mixing speed at fixed mixing time according to a two‐factor and three‐level factorial design. The extruded strands were compression molded under comparable conditions, and their volume resistivity values indicated differences of about 14 orders of magnitude as well as big differences in the state of MWNT agglomerate dispersion (evaluated as macrodispersion index) are observed. The results indicate that mixing at high melt temperature and high speed can lead to the composites having low resistivity and high dispersion index at low mixing energy input. The influence of compression molding parameters was investigated on precompounded PC composites containing 1 and 2 wt % MWNT. Compression molding parameters such as temperature, time, and speed were varied according to a three‐level and three‐factor factorial design. By adjusting compression molding parameters, the volume resistivity of PC with 1 wt % MWNT composites can be varied over eight orders of magnitude, whereas for 2 wt % MWNT, the variation was within one decade. The electrical volume resistivity results indicate the highest influence of the compression molding temperature followed by time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synergistic Effect of Halloysite Nanotubes and MA-g-PE on Thermo-Mechanical Properties of Polycarbonate-Cyclic Olefin Copolymer Based Nanocomposite

This article explores the synergistic effect of halloysite nanotubes along with maleic anhydride grafted polyethylene on the physical, mechanical, and thermo-mechanical properties of polycarbonate/cyclic olefin copolymer polymer blend system. Halloysite nanotubes filled polycarbonate/cyclic olefin copolymer blend nanocomposites were prepared in the presence and absence of polymeric compatibilizer by melt blending. Besides the constructive outcome of nanotubular fillers, the maleic anhydride grafted polyethylene played a complementary role in improving the properties of the nanocomposites. Structural changes of blend matrix, nanofiller distributions, nanofiller-polymer matrix interaction, nucleating effect, storage modulus, and thermal stability were widely investigated with various sophisticated instruments.     

钼酸钠复合缓蚀剂对碳钢缓蚀性研究

制备了钼酸钠复合缓蚀剂。利用静态失重法测定了其在盐酸介质中碳钢的缓蚀腐蚀速度和缓蚀效率 ,研究了碳钢在盐酸介质中的腐蚀动力学特征。结果表明 ,钼酸钠复合缓蚀剂对碳钢具有良好的缓蚀能力 ,缓蚀率为 95% ,且随温度升高而增大。     

环氧树脂/蒙脱土纳米复合涂料防腐性能的研究进展

环氧树脂涂料在防腐领域中应用广泛,但仍需进行改性以满足应用需求,一个比较经济、有效的途径就是添加纳米填料。蒙脱土片层分散在环氧树脂基料中时,能有效阻隔腐蚀性介质穿过涂膜,进而提高纳米复合涂料的防腐性能。简单介绍了蒙脱土的结构,环氧树脂/蒙脱土纳米复合涂料的制备方法。综述了近年来环氧树脂/蒙脱土纳米复合涂料防腐性能的研究进展。     

Electrical conductivity modeling of carbon black/polycarbonate,carbon nanotube/polycarbonate,and exfoliated graphite nanoplatelet/polycarbonate composites

Adding conductive carbon fillers to electrically insulating thermoplastic polymers increases the resulting composite's electrical conductivity, which would enable them to be used in electrostatic dissipative and semiconductive applications. In this study, varying amounts of carbon black (CB: 2 to 10 wt %), multiwalled carbon nanotubes (CNT: 0.5 to 8 wt %), or exfoliated graphite nanoplatelets (GNP: 2 to 15 wt %) were added to polycarbonate (PC) and the resulting composites were tested for electrical conductivity (EC = 1/electrical resistivity). The percolation threshold was ～ 1.2 vol % CNT, ～ 2.4 vol % CB, and ～ 4.6 vol % GNP. In addition, three EC models (Mamunya, additive, and general effective media) were developed for the CB/PC, CNT/PC, and GNP/PC composites. The general effective media (GEM) model showed the best agreement with the experimental results over the entire range of filler concentrations (above and below the percolation threshold) for all three composite systems. In addition, the GEM model can be easily adapted for composites containing combinations of different conductive fillers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Research Progress on Properties and Applications of Polymer/Clay Nanocomposite

This review covers significant properties and applications of nanoclays in polymer-based nanocomposites with special emphasis on future potential. Various strategies have been adopted for nanocomposite synthesis including delamination of nanoclays through melt shearing, in situ polymerization, and sol–gel method. Proper dispersion of nanoclay results in improved properties of bulk polymer (thermal stability, mechanical strength, gas barrier, and flame retardancy). Light weight, low cost, and improved physical properties of polymer/clay materials increase their demand in modern material industries (aerospace, automobile, barrier materials, construction, and biomedical). Due to extensive use of these nanocomposites in technical fields, there are still many stones left unturned.     

SiC/ZTM Nanocomposite with Needlelike Mullite Grains and Enhanced Mechanical Properties

Zirconia-toughened mullite (SiC/ZTM) nanocomposites were prepared by a chemical precipitation method. The samples showed good sinterability and could be densified to >98.7% of the theoretical density at 1350°–1550°C. Because of the addition of mullite seeds in the starting powder and the pinning effects of ZrO₂ and SiC particles on mullite grain growth, a fine-grained microstructure formed. Mullite grains were generally equiaxed for the sample sintered at 1400°C; whereas, for the sample sintered at 1550°C, most mullite grains took a needlelike morphology, and SiC particles were primarily located within mullite grains. The strength and toughness increased with the increasing sintering temperature, and reached their respective maximum of 780 MPa and 3.7 MPa·m^1/2 for the sample sintered at 1550°C.     

粘土/SBR/BIIR纳米复合材料的结构与性能

采用溴化丁基橡胶(BIIR)与粘土/SBR复合胶制备粘土/SBR/BIIR复合材料,并对其结构与性能进行研究.结果表明:粘土/SBR/BIIR并用胶为以BIIR为连续相、以SBR为分散相的海岛结构,并且粘土基本分散于SBR分散相中,所制备的复合材料为隔离型纳米复合材料;BIIR与SBR的相容性不好,热力学上基本不相容;...     

Corrosion Resistance and Electrical Conductivity of Hybrid Coatings Obtained from Polysiloxane and Carbon Nanotubes by Electrophoretic Co-Deposition

Nanocomposites developed based on siloxanes modified with carbon nanoforms are materials with great application potential in the electronics industry, medicine and environmental protection. This follows from the fact that such nanocomposites can be endowed with biocompatibility characteristics, electric conductivity and a high mechanical durability. Moreover, their surface, depending on the type and the amount of carbon nanoparticles, may exhibit antifouling properties, as well as those that limit bacterial adhesion. The paper reports on the properties of polysiloxane (PS) and carbon nanotubes (CNT) nanocomposite coatings on metal surfaces produced by the electrophoretic deposition (EPD). A comparison with coatings made of pure PS or pure CNT on the same substrates using the same deposition method (EPD) is provided. The coatings were examined for morphology and elemental composition (SEM, EDS), structural characteristics (confocal Raman spectroscopy), electrical conductivity and were tested for corrosion (electrochemical impedance spectroscopy-EIS, potentiodynamic polarization-PDP). The results obtained in this study clearly evidenced that such hybrid coatings conduct electricity and protect the metal from corrosion. However, their corrosion resistance differs slightly from that of a pure polymeric coating.     

Nano‐/Microscale Investigation of Tribological and Mechanical Properties of Epoxy/MWNT Nanocomposites

The effects of MWNT content and aspect ratio on the properties of epoxy‐based nanocomposites are investigated using nanoindentation and nanoscratch methods. The Halpin‐Tsai model for predicting the elastic modulus and hardness is modified to include the effective aspect ratio factor. The modified model predicts the experimental results more accurately. The frictional behavior is investigated and a new equation is proposed that correlates the ploughing friction with the plasticity index. The dispersion state of MWNTs and the surface features of residual grooves are investigated using scanning electron micrographs and AFM profiles. The mechanisms of improvements in the properties are also discussed.

     

Effect of Dispersants on the Electrophoretic Deposition of Hydroxyapatite‐Carbon Nanotubes Nanocomposite Coatings

Isopropanolic Suspensions of HA nanoparticles (20 g/L) plus various concentrations of carbon nanotubes (CNTs) were prepared using Tris and triethanolamine as dispersant. The positively charged HA nanoparticles were heterocoagulated on the negatively charged CNTs and generated the HA‐CNT composite particles with net positive surface charge. The heterocoagulation was more intensive in dispersant‐containing suspensions (DCS) due to the higher zeta potential of HA nanoparticles in them. HA‐CNTs particles can be rotated and aligned parallel to electric field as a result of torque exerted on them due to the generation of a dipole moment in CNTs during electrophoretic deposition (EPD). The mobility of HA‐CNTs particles aligned parallel to electric field is ≈50% higher than that of HA nanoparticles leading to the faster EPD from DCS when CNTs are added into them. CNTs more efficiently reinforced the coatings deposited from DCS due to the stronger electrostatic bonding between CNTs and HA nanoparticles in them.     

碳纳米管改性填料对氟碳涂料性能的影响

采用混合酸和表面活性剂对碳纳米管表面进行改性处理,利用改性碳纳米管与不同的填料构造复合填料,并与FEVE氟碳树脂合成了碳纳米管改性复合氟碳材料,并将其涂覆在陶瓷基底上形成氟碳涂层。采用红外光谱（FTIR）对表面改性后的碳纳米管进行了表征分析,用扫描电镜（SEM）、接触角测量仪等仪器观察和测试了纳米复合氟碳涂层表面的微观结构及疏水性。研究结果表明：用混合酸和表面活性剂改性碳纳米管,碳纳米管的缠绕、团聚现象得到明显的改善,提高了其在氟碳树脂体系中的分散性能;当改性碳纳米管的量为0.75 g时,涂层的憎水性能较好。     

聚苯胺接枝多壁碳纳米管的制备及热电性能

通过原位聚合,将聚苯胺接枝到多壁碳纳米管的表面,制备了聚苯胺/碳纳米管纳米纤维。聚苯胺均匀地包覆在碳纳米管表面,当苯胺与碳纳米管投料比为1∶1时,包覆层厚度约为15 nm。聚苯胺/多壁碳纳米管的电导率和塞贝克系数随温度升高而增大,且增大碳纳米管含量同时提高了复合材料的电导率和塞贝克系数,改善了功率因子。     

Preparation and characterization of alkylated carbon nanotube/polyimide nanocomposites

BACKGROUND: The development of carbon nanotube‐reinforced composites has been impeded by the difficult dispersion of the nanotubes in polymers and the weak interaction between the nanofiller and matrices. Efficient dispersion of carbon nanotubes is essential for the formation of a functional nanotube network in a composite matrix. RESULTS: Multiwalled carbon nanotubes (MWNTs) were incorporated into a polyimide matrix to produce MWNT/polyimide nanocomposites. To disperse well the MWNTs in the matrix and thus improve the interfacial adhesion between the nanotubes and the polymer, ‘branches’ were grafted onto the surface of the nanotubes by reacting octadecyl isocyanate with carboxylated MWNTs. The functionalized MWNTs were suspended in a precursor solution, and the dispersion was cast, followed by drying and imidization to obtain MWNT/polyimide nanocomposites. CONCLUSION: The functionalized MWNTs appear as a homogeneous dispersion in the polymer matrix. The thermal stability and the mechanical properties are greatly improved, which is attributed to the strong interactions between the functionalized MWNTs and the polyimide matrix. Copyright © 2009 Society of Chemical Industry     

聚己内酯静电纺丝纳米纤维与环氧树脂复合涂层防腐性能的研究

利用静电纺丝法在Q345钢表面制备聚己内酯(PCL)与缓蚀剂二巯基苯并噻唑(MBT)的纳米纤维膜PCL/MBT,然后在其表面旋涂环氧树脂(EP),得到复合涂层。通过电化学阻抗谱技术研究了复合涂层的防腐蚀性能。结果表明:在温度为25 ℃、湿度20%、纺丝电压15 kV、接收距离18 cm、V(氯仿)∶V(丙酮)=2∶3的条件下,PCL质量分数为12%,MBT质量浓度为0.01 g/mL时,静电纺丝得到的纳米纤维表面光滑,粗细均匀。电化学测试结果表明:EP/PCL/MBT复合涂层的防腐性能优于EP/PCL或EP涂层。     

Preparation and Combustion Properties of Flame Retardant Nylon 6/Montmorillonite Nanocomposite

Flame retardant Nylon 6 (PA6)/montmorillonite (MMT) nanocomposites have been prepared using direct melt intercalation technique by blending PA6, organophilic clay and conventional fire retardants, such as the melamine cyanurate (MCA) and the combination of decabromodiphenyl oxide (DB) and antimony oxide (AO). Their morphology and combustion properties are characterized by XRD, transmission electron microscopy (TEM), UL‐94 test and Cone Calorimeter experiments. The flame retardant nanocomposites with MCA or DB and AO show lower heat release rate (HRR) peak compared to that of conventional flame retardant PA6. Meanwhile, the synergetic effect was studied between clay and DB‐AO.

TEM of PA‐n nanocomposite.     

Thermal conductivity and dynamic mechanical property of glycidyl methacrylate‐grafted multiwalled carbon nanotube/epoxy composites

The well dispersed multiwalled carbon nanotube (MWCNT)/epoxy composites were prepared by functionalization of the MWCNT surfaces with glycidyl methacrylate (GMA). The morphology and thermal properties of the epoxy nanocomposites were investigated and compared with the surface characteristics of MWCNTs. GMA‐grafted MWCNTs improved the dispersion and interfacial adhesion in epoxy resin, and enhanced the network structure. The storage modulus of 3 phr GMA‐MWCNTs/epoxy composites at 50°C increased from 0.32 GPa to 2.87 GPa (enhanced by 799%) and the increased tanδ from 50.5°C to 61.7°C (increased by 11.2°C) comparing with neat epoxy resin, respectively. Furthermore, the thermal conductivity of 3 phr GMA‐MWCNTs/epoxy composite is increased by 183%, from 0.2042 W/mK (neat epoxy) to 0.5781 W/mK. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011