多壁碳纳米管改性水泥基复合材料的性能研究

通过试验研究了多壁碳纳米管(MWCNTs)掺量对水泥净浆的力学性能、水化特性、凝结时间、孔隙分布等性能的影响,并采用SEM(扫描电镜)观察与分析了MWCNTs改性水泥净浆的微观形貌。结果表明,MWCNTs的掺入会降低水化过程中矿物的溶解速率,因而延缓了水泥的水化进程;在适宜的掺量范围内,MWCNTs能够有效提升水泥净浆的力学强度,但当其掺量过高时,反而会对力学强度造成不利影响;MWCNTs在水泥净浆中能够分散均匀并降低水泥净浆的孔隙率,使其变得更加密实。     

Cu-BTC改性水泥基复合材料的微观结构和力学性能

以金属-有机骨架化合物(Cu-BTC)为改性剂,对水泥基复合材料进行了改性,获得了具有规整蛛网状结构的改性水泥基复合材料,并运用FT-IR、XRD、SEM、EDs等对其结构及性能进行了分析.实验结果表明:引入Cu-BTC并不会改变水化产物的构成,而Cu-BTC含有的活性—COOH能够诱导水化产物形成生长位点,水化产物后...     

碳纳米管-水泥基复合材料的力学性能和微观结构

研究了掺碳纳米管水泥砂浆的力学性能和微观结构,并与掺碳纤维水泥砂浆的性能进行了对比。低含量的碳纳米管-水泥复合材料具有良好的抗压强度和抗折强度。用扫描电镜对碳纳米管-水泥复合材料以及碳纤维-改性水泥复合材料的微观结构进行了分析。结果表明：复合材料中碳纳米管表面被水泥水化产物包裹,同时碳纳米管水泥砂浆的结构密实。碳纤维表面光滑,在碳纤维与水泥石之间存在明显裂缝。孔隙率测试结果表明碳纳米管的掺入改善了材料的孔结构。     

多壁碳纳米管水泥基复合材料的压敏性能研究

采用聚羧酸系减水剂分散多壁碳纳米管（ MWCNTs ）,利用四电极法研究了 MWCNTs 掺量对28 d 龄期MWCNTs水泥基复合材料导电特性和在循环荷载作用下压敏性能的影响以及不同最大加载力和加载速率下材料压敏性能的变化。研究表明：随 MWCNTs 掺量的增加,复合材料的电阻率逐渐降低,极化时间逐渐减少。当MWCNTs的掺量在0．06wt％～0．3wt％范围时,复合材料电阻率的变化最大,在循环荷载作用下也表现出良好的压敏性。当加载至试块破坏的情况下,最大电阻变化率可达到70％。随着加载力和加载速率的增加,电阻率的变化率均逐渐变大。本项研究对于实现混凝土材料的智能化以及工程结构检测的实时化具有重要意义。     

多壁碳纳米管分散性对水泥基材料导电性能和电热特性的影响

采用分散剂、超声处理及离心机分离作用,得到分散均匀、稳定状态的多壁碳纳米管(MWCNTs)悬浮液和分散不均匀、团簇状态的MWCNTs沉淀,分别将这两种状态的MWCNTs掺入水泥净浆中,研究MWCNTs分散性对水泥基材料电学性能和电热特性的影响.结果表明:MWCNTs在水泥基体中分散均匀时,随MWCNTs掺量的增加试块电阻率下降;当MWCNTs在水泥基体中分散不均匀时,试块的导电性与MWCNTs掺量没有明确的相关性.MWCNTs水泥净浆的电阻率均随测试温度的升高不断降低,当温度超过80℃时,电阻率趋于恒定,并且MWCNTs分散均匀时,水泥净浆电阻率受温度影响的程度随MWCNTs掺量增高而减小;MWCNTs在基体中分散效果好时,水泥净浆因通电引起的升温速率和幅度随着MWCNTs掺量增大而提高.     

掺钢渣水泥基复合材料的吸波性能

钢渣中含有大量的铁的氧化物,且以多种状态存在.在1～18GHz内采用弓形反射法研究钢渣掺入水泥后的吸波性能.结果显示:吸收峰的位置基本不受养护时间和掺量的影响,但随试样厚度的增加会表现出向低频区移动:随试样厚度的增加,在低频区1～8 GHz波段范围内,最大吸收率从23 dB逐渐降低到7.5 dB,而在高频区10～18 GHz波段范围内,吸收率先逐渐增加达到最大值后再降低;当掺30%(质量分数)粉磨60 min的钢渣,复合材料的厚度为25 mm,养护285 d时,在13～18 GHz波段内吸收率最大达到12 dB.大于8 dB的带宽为5 GHz,表现出较好的吸波性能.     

碳纳米管水泥基复合材料的研究进展

近年来,碳纳米管(CNTs)在传统胶凝材料中的应用愈来愈受到人们的重视。通过添加适量的CNTs,可以使胶凝材料的一些性能得到有效改善。本文综述了国内外有关CNTs在水泥基材料中的应用研究进展,主要探讨了CNTs对水泥基材料的力学性能、耐久性及微观结构的影响,掺加活性物质对CNTs/水泥基复合材料性能的影响,并且总结了当前研究中所存在的一些问题,为今后的研究前景提出了一些建议。     

碳纳米管增强水泥净浆的动态力学特性EI北大核心CSCD

利用分离式Hopkinson压杆(SHPB)装置对不同掺量(占水泥的质量分数)碳纳米管(CNTs)的水泥净浆试样在冲击荷载下的动力学特性展开研究,并利用扫描电子显微镜揭示了含CNTs水泥净浆的微观形貌特征。结果表明:在恒定冲击荷载下,试样的动态抗压强度、弹性模量和峰值韧度均随CNTs掺量的增加呈现出先增加后减小的趋势;CNTs掺量为0.1%时,三者达到最大值,与空白对照试样相比,其增幅分别为34.1%、70.0%和15.4%;试样的破坏程度表现出相反的变化规律,0.1%CNTs掺量的试样破碎程度最低,分形维数较空白试样减小了22.3%;适量的CNTs可改善水泥基体的孔径分布,对孔洞、裂缝进行填充与桥接,使其更加致密,但当其掺量过高极易发生团聚,降低基体的力学性能。     

聚合硫酸铝改性低碱度水泥性能研究

以水泥、硅灰和粉煤灰为主要胶凝材料制备的低碱度水泥可应用于放射性焚烧灰的固化,但其存在早期强度发展慢、后期强度不高的问题。本文以聚合硫酸铝作为添加剂激发火山灰材料反应活性,通过测定不同掺量聚合硫酸铝加入后固化体的抗压强度、孔隙率及pH值变化,并结合水化产物组成与含量、水化放热特性等表征手段,分析了聚合硫酸铝对低碱度水泥早期水化过程的影响规律和作用机理。结果表明:掺入聚合硫酸铝可以显著提高低碱度水泥固化体的早期抗压强度,使水化放热峰提前,促进了火山灰反应的发生,提高了水化产物的生成量,使微观结构更加密实,同时有效降低试样的早期碱度,有利于抑制焚烧灰中活性铝的腐蚀反应。     

多壁碳纳米管／环氧树脂复合材料性能研究

采用物理机械方法与化学方法相结合的手段,制备了多壁碳纳米管（MWNTS）／环氧树脂（Epoxy）复合材料。通过力学拉伸试验测试了MWNTs/Epoxy复合材料拉伸强度和拉伸模量与MWNTS添加量的关系,利用扫描电镜（SEM）分析了MWNTS／Epoxy复合材料的拉伸断面,并用表面电阻测试仪对所制备的碳纳米管复合材料进行了电学性能测试。结果表明：经过化学酸化的方法处理后的MWNTS在复合材料中的分散得到了改善,力学性能也得到了明显的提高,但酸处理后的复合材料的电学性能明显低于未处理的复合材料。     

Mechanical behavior and microstructure of cement composites incorporating surface-treated multi-walled carbon nanotubes

Multi-walled carbon nanotubes after modified by using a H₂SO₄ and HNO₃ mixture solution were added to cement matrix composites. The mechanical properties of the newly formulated composites were analyzed, and the results show that the treated nanotubes can improve the flexural strength, compressive strength, and failure strain of cement matrix composites. The porosity and pore size distribution of the composites were determined by using Mercury intrusion porosimetry, and it is observed that the addition of carbon nanotubes can fine the pore size distribution and decrease porosity. The phase composition was characterized with Fourier transform infrared spectroscopy. It is found that there are interfacial interactions between carbon nanotubes and the hydrations (such as C-S-H and calcium hydroxide) of cement, which will produce a high bonding strength between the reinforcement and cement matrix. The mineralogy and microstructure were analyzed by using scanning electron microscope. It is shown that carbon nanotubes act as bridges across cracks and voids, which guarantees the load-transfer in case of tension.     

碳纳米管/丙烯酸酯橡胶复合材料的制备及性能研究

采用自制的大分子表面改性剂对多壁碳纳米管(MWNTs)进行表面改性,制备改性MWNTs/丙烯酸酯橡胶(ACM)复合材料,研究改性MWNTs用量对复合材料性能的影响,并与炭黑补强的ACM性能进行对比.结果表明:用MWNTs填充ACM制备的材料,其性能远优于炭黑补强的ACM橡胶的性能;随着改性MWNTs用量的增大,复合材料...     

Capacitance properties of multi-walled carbon nanotubes modified by activation and ammoxidation

Catalytic multi-walled carbon nanotubes were modified by KOH activation at 800 °C and/or ammoxidation at 350 °C, and the effect of these treatments on the physicochemical and electrochemical properties was investigated. Whereas texture is moderately changed by ammoxidation, the chemical composition is significantly modified due to the formation of various nitrogen containing groups. The influence of nitrogenated functionality (pyridine, pyridone, NH) on charge accumulation is considered in full electrochemical capacitors, as well as in positive and negative electrodes separately, using acidic (4 mol L⁻¹ H₂SO₄) and alkaline (7 mol L⁻¹ KOH) electrolytes. The presence of nitrogen in the carbon network, especially in the form of pyridone/pyrrolic (N5) and/or pyridine (N6) groups, affects the electron density and enhances the charge affinity of the carbon material. It seems that the nitrogen groups improve particularly the capacitance performance of the negative electrode operating in alkaline medium. Besides the nitrogenated groups, the oxygenated functionality plays also an important role for the ammoxidized nanotubes. Generally, a few-fold increase of capacitance was observed in the N-enriched carbon nanotubular samples. Apart of this capacitance improvement, the presence of nitrogen in the carbon network limits significantly the leakage current and diminishes the self-discharge of supercapacitors.     

Structure and magnetic properties of multi-walled carbon nanotubes modified with cobalt

The magnetic properties of multi-walled carbon nanotubes (MWCNTs) modified with cobalt nanoparticles were studied in the temperatures and magnetic field range of (4.2–290) K and (0.03–5) T, respectively. Nanoparticles of cobalt encapsulated inside MWCNTs were obtained by using the chemical vapor deposition technique. The low temperature SQUID magnetization measurements were supplemented with structural investigations by means of high-resolution transmission electron microscopy, scanning electron microscopy as well as thermogravimetric and X-ray diffraction analysis. X-ray diffraction revealed the presence of MWCNTs, f.c.c. Co and h.c.p. Co phases. The magnetic characterization provided the remanent magnetization value (M_R) of about 0.07 emu/g (∼40% of the saturation moment), while the coercive field (H_C) value amounts to 600 Oe. Both parameters M_R and H_C slightly decrease with the rise of temperature. The substantial magnetization increase observed at low temperatures suggests the existence of nano Co clusters (in the atomic scale size).     

Dielectric properties of epoxy composites with modified multiwalled carbon nanotubes

We report here a high dielectric percolative polymer nanocomposite, fabricated by a combination of triethylene-tetramine (TETA) modified multiwalled carbon nanotube (named as TETA-MWNT) within epoxy resin matrix. In this composite system, with various TETA-MWNT volume fractions, the dielectric constant (K) is well fitted by the scaling law of the percolation theory with the percolation threshold f _c is 0.042 and the critical exponent p is 0.786. At 1,000 Hz of room temperature, the value of the dielectric constant is as high as 421 with the TETA-MWNT content of 4.14vol%, which is almost 60 times higher than that of epoxy resin. In contrast, a simple blend of pristine MWNT in epoxy composite shows evident lower dielectric constant and much higher loss with the same volume fraction.     

Study on the properties of multi-walled carbon nanotubes reinforced poly (vinyl alcohol) composites

Nanocomposite films based on polyvinyl alcohol(PVA) and multi-walled carbon nanotubes (MWCNTs) at different weight ratios (i.e.0.0,0.5, 1.0,1.5, 2.0 wt%), were prepared by dispersion techniques. Cationic geminisurfactant and its monomeric form (0.01 wt%) were used as dispersants to achieve homogeneous and stable dispersionof CNTs in water and subsequent PVA/CNTs nanocomposites. Surface charge of CNTs in aqueous suspension with addition of the used dispersants were investigated by measuring its zeta potential. The structural and interaction studies have been analyzed from X-ray diffraction (XRD) and Raman spectroscopy. The effect of the used surfactantson the separation and distribution of CNTs in PVA matrix was studied by visual characterization based on scanning electron microscopy (SEM). Thermal, mechanical and electrical properties of the prepared nanocomposites were evaluated and the results were discussed in relation with the CNTs content and surfactant type as dispersant. Surfactant effect improved the dispersion homogeneity of CNTs (at 1.0 wt%) within the polymer matrix. The physical interaction between. CNTs and PVA macromolecular chains resulting in nanocomposites with largely enhanced properties compared to those prepared with higher filler loading by avoiding the agglomeration phenomenon of nanotubes. On the other hand, the addition of CNTs by content up to 2 wt%, increases the electrical conductivity to be 10^?6 Scm^?1 at room temperature which highly recommends such composites to be used in electrostatic dissipation applications upon using gemini surfactant. Furthermore, useful nanosized capacitor structure based onnanocomposites containing its monomeric form, characterized by high permittivity and low dielectric loss, can be formed.     

碳纳米管改性聚氨酯复合材料

用原位聚合法制备两组聚氨酯(PUR)/碳纳米管(CNTs)复合材料.一组是在超声波作用下将CNTs直接和PUR复合;另一组是将硅烷偶联剂处理的CNTs在超声波作用下与PUR原位聚合制备PUR/CNTs复合材料.探讨了CNTs含量对复合材料电性能的影响,在w(CNTs)为1.0%时可用作抗静电材料.经硅烷偶联剂处理的CN...