氧化石墨烯对水泥水化产物及聚集状态的调控作用

通过对石墨的氧化及超声波分散制备了氧化石墨烯(GO)纳米片层,采用FTIR、XPS、SEM、AFM对其结构进行了表征。测试结果表明:GO纳米片层尺寸为100~800 nm,GO上羟基和羧基的质量分数分别为22.1%和29.4%。将GO掺入水泥基复合材料,在GO的加入质量为水泥质量的0.03%时,水泥基体主要由多面体状晶体通过交织、嵌入等方式聚集而成,形成了具有花型形貌的微观结构,与空白样比较,其28 d时平均抗折强度和抗压强度分别增加了93.9%和80.0%。     

氧化石墨烯对水泥基复合材料微观结构的调控作用及对抗压抗折强度的影响

通过氧化法制备得到氧化石墨烯（GO）,通过GO与丙烯酸（AA）和丙烯酰胺（AM）进行插层聚合反应制备得到插层复合物GO/P（AA-AM）。检测结果表明,GO在插层复合物中具有较小的尺寸和均匀的分布,将GO/P（AA-AM）掺入水泥基复合材料中,发现水泥水化产物成为规整的针状、棒状或多面体状晶体,并且能够聚集形成具规整形貌的微观结构和宏观结构,水泥基复合材料中的裂缝及有害孔洞比对照样品明显减少,其抗压强度和抗折强度比对照样品有明显提高。提出了GO纳米片层对于水泥基复合材料规整结构的调控机理,认为GO纳米片层及活性基团能够促进水泥化产物形成规整形状的水化晶体,最初形成的水化晶体成为后续水化晶体形成的模板,通过晶体的生长最终形成规整水化晶体及规整的微观结构和宏观结构。     

氧化石墨烯在水泥基材料中的作用研究综述

结合国内外氧化石墨烯在水泥基材料中的应用研究,分析了氧化石墨烯在水泥基材料中的作用机理,并通过总结国内外文献中氧化石墨烯水泥基材料的性能改善。综述了现阶段氧化石墨烯在水泥基材料中的研究动态,为后续氧化石墨烯在水泥基材料中的研究提供借鉴。     

氧化石墨烯分散方式对水泥基材料性能的影响

氧化石墨烯(GO)在水泥基材料应用中存在分散不均匀、易团聚问题,影响其改善水泥基性能的效果.为提高GO的作用效果,采用聚羧酸系高效减水剂(PC)为分散剂,提出PC-GO在水、水泥浆中的分散机理模型.将PC-GO溶液超声分散0 min、10 min、30 min、60 min和120 min,通过激光粒度仪、原子力显微镜(AFM)和扫描电镜(SEM)等,研究不同分散时间下GO的分散效果、分散稳定性以及对力学性能的影响.研究表明,在低分散程度时,分散时间越长,分散效果及稳定性越好,而过度超声波处理则使分散效果劣化,流动度随分散时间增加而降低;当分散时间大于30 min时,早龄期的抗压和抗折强度分别提高了18.68％～30.87％和20.31％～31.22％.根据研究结果,GO的分散时间建议为30～60 min.     

氧化石墨烯对水泥水化进程及其主要水化产物的影响EI北大核心CSCD

研究了氧化石墨烯（GO）对水泥水化进程及其主要水化产物氢氧化钙（CH）、水化硅酸钙凝胶（C-S-H）的影响。采用原子力显微镜、透射电镜等对所用GO进行了表征,采用水化热、X射线衍射分析以及热重分析等方法对不同GO掺量的新拌水泥浆体水化程度以及水化产物含量等进行了测量。结果表明：GO的掺入对水泥水化进程并无明显影响,即GO并不存在促进水化的作用,但是GO的掺入可以影响水化产物尤其是氢氧化钙的结晶过程和形态;GO对水泥浆体硬化后形成的凝胶孔特征有重要影响,随着GO掺量的增加,能够使凝胶孔中存有更多的自由水,并在一定程度上细化、封闭孔结构;GO的存在不仅对六方片状晶体的生成有明显抑制作用,并且能够细化晶体氢氧化钙的尺寸。     

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,水化产物后续以Cu-BTC的生长过程为模板,两者协同竞争,最终形成具有大面积规整均匀的蛛网状微观形貌.力学性能表征表明:当Cu-BTC的质量分数为2.0％时,改性水泥基复合材料28 d的抗压强度最高达28.80 MPa,较空白样品提高了54.84％,这说明Cu-BTC的模板化调控作用有利于改善水泥基复合材料的力学性能.     

杀白蚁剂对水泥基材料强度与微观结构的影响

采用扫描电镜、X射线衍射技术研究了三种杀白蚁剂对水泥基材料的水化产物及其微观结构的影响,并结合掺杀白蚁剂水泥基材料的强度,探究两者之间的内在联系.结果 表明:杀白蚁剂的掺入会降低水泥基材料的强度,且随着杀白蚁剂浓度的提高,强度会逐渐降低.各试验组的主要水化产物均为Ca(OH)2和CaCO3,掺入杀白蚁剂并不会产生新的水化产物.与此同时,掺入较高浓度杀白蚁剂时,有利于促进水泥基材料的早期水化.相比于联苯菊酯和毒死蜱杀白蚁剂,吡虫啉杀白蚁剂对水泥基材料的影响更为严重.     

减缩剂对水泥基材料水化和孔结构的影响

通过对水泥净浆水化放热量、Ca(OH)2的含量和化学结合水量及水泥砂浆的孔结构的测定,研究减缩剂对水泥基材料水化和孔结构的影响.结果表明:减缩剂会延缓水泥的水化,且随着龄期的发展,延缓作用渐弱.具体表现为减缩剂会降低水泥水化放热的峰值,延迟峰值出现的时间,减小水化放热量;减缩剂能够减小水泥净浆的化学结合水量;龄期为3d时,掺减缩剂的净浆中Ca(OH)2的含量明显低于空白样的,28d时与空白样的相当;减缩剂能够减小水泥砂浆中多害孔和有害孔的孔体积,增加无害孔的孔体积.另外还对减缩剂在水泥基材料中存在的形态提出设想.     

还原氧化石墨烯增强水泥基复合材料微观结构及力学性能

采用水热还原法制备了不同还原程度的还原氧化石墨烯(RGO),并将其添加到水泥浆体中,制得石墨烯增强水泥基复合材料。采用傅里叶变换红外光谱(FT-IR)、力学性能测试仪、扫描电子显微镜(SEM)对氧化石墨烯(GO)还原程度及水泥基复合材料的力学性能和微观结构进行测试。结果表明,在120℃水热条件下,控制不同还原时间可以得到不同还原程度的RGO;随着GO还原程度的提高,复合材料力学强度不断增加;RGO可使水泥更加密实,降低了水泥浆体的孔隙率,对水泥基复合材料起到增强增韧的作用。     

Reduced graphene oxide/carbon nanotubes reinforced calcium phosphate cement

Improving the mechanical properties of calcium phosphate cement (CPC) will be helpful for expanding its application range in the treatment of bone defect. In this work, reduced graphene oxide (RGO), which has two-dimensional structure and excellent mechanical properties, and carbon nanotubes (CNTs) were used as toughening materials collectively, to enhance the mechanical properties of CPC. Setting time, morphology and mechanical properties of CPC were analyzed. The two dimensional structure of RGO could increase the interface area between RGO and substrate, which achieved an effective transfer of load between substrate and RGO. Moreover, by reasons of bridging cracks, preventing crack extension, pulling out from substrate and interface debonding, the flexural strength and compressive strength of CPC were increased by 67.1% ± 4.8% and 76.4% ± 10.6% respectively. Therefore, the CPC composite we studied has potential to be used as load-bearing substitution in bone defects.     

The effects of graphene oxide on the properties and drug delivery of konjac glucomannan hydrogel

Konjac glucomannan (KGM) hydrogel has good potential application in food and medical science, although to achieve this, the physical and mechanical properties need further improvement. In this study, graphene oxide (GO) was used to improve the functionality of KGM hydrogel. KGM/GO hydrogels were prepared by freezing the alkaline KGM/GO sols. Rotational rheometer was used to study the rheological properties of different alkaline KGM/GO sols. Fourier transform infrared, Raman, differential scanning calorimetry, thermogravimetric analyses, and scanning electron microscopy were used to evaluate the structure and properties of the hydrogels. In addition, different pH solutions and an in vitro assay were used to study the swelling property and the release behavior of KGM/GO hydrogels, respectively. The result revealed strong hydrogen‐bond interaction between KGM and GO. The incorporation of GO highly improved the gel properties of KGM/GO sol, higher thermal stability, and more compact structure of KGM/GO hydrogels. KGM/GO hydrogels showed better swelling properties in deionized‐distilled water and pH 7.2 PBS. The release of 5‐aminosalicylic acid (5‐ASA) from KGM/GO (KG4) hydrogel was different in various pH media, but the initial burst release effect was very severe. Therefore, incorporation of GO have a good potential in enhancing the properties of KGM hydrogel, but KGM/GO hydrogel is not an ideal carrier for 5‐ASA release. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45327.     

氧化石墨烯液晶相结构的调控及应用进展

氧化石墨烯液晶（GOLCs）是氧化石墨烯薄片分散在水或极性有机溶剂中形成的宏观介晶有序、微观各向异性的液晶相,在自组装膜、储能、液晶显示器和超强纤维等领域展现良好的应用前景。本文首先介绍了氧化石墨烯液晶具有向列相、层状相和手性相等结构特征;具体综述了氧化石墨烯液晶相变的影响因素、调控途径及其原理,包括氧化石墨烯的尺寸及其分布、氧化石墨烯的氧化程度、氧化石墨烯在溶液中的质量/体积分数、溶剂的极性、溶液的pH以及添加盐的种类、浓度,外界施加的电场或磁场;最后简单介绍了氧化石墨烯液晶在电化学及其他方面的潜在应用。本文为调控氧化石墨烯液晶的相结构、开发多功能氧化石墨烯液晶及拓宽氧化石墨烯液晶的应用领域提供了理论指导。     

Effect of graphene oxide on the behavior of poly(amide‐6‐b‐ethylene oxide)/graphene oxide mixed‐matrix membranes in the permeation process

Polyether‐block‐amide (Pebax)/graphene oxide (GO) mixed‐matrix membranes (MMMs) were prepared with a solution casting method, and their gas‐separation performance and mechanical properties were investigated. Compared with the pristine Pebax membrane, the crystallinity of the Pebax/GO MMMs showed a little increase. The incorporation of GO induced an increase in the elastic modulus, whereas the strain at break and tensile strength decreased. The apparent activation energies (E_p) of CO₂, N₂, H₂, and CH₄ permeation through the Pebax/GO MMMs increased because of the greater difficulty of polymer chain rotation. The E_p value of CO₂ changed from 16.5 kJ/mol of the pristine Pebax to 23.7 kJ/mol of the Pebax/GO MMMs with 3.85 vol % GO. Because of the impermeable nature of GO, the gas permeabilities of the Pebax/GO MMMs decreased remarkably with increasing GO content, in particular for the larger gases. The CO₂ permeability of the Pebax/GO MMMs with 3.85 vol % GO decreased by about 70% of that of the pristine Pebax membrane. Rather than the Maxwell model, the permeation properties of the Pebax/GO MMMs could be described successfully with the Lape model, which considered the influence of the geometrical shape and arrangement pattern of GO on the gas transport. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42624.     

Influence of molecular weight of polymer matrix on the structure and rheological properties of graphene oxide/polydimethylsiloxane composites

The structure and rheological properties of graphene oxide (GO)/polydimethylsiloxane (PDMS) composites are examined as the molecular weight of PDMS and concentration of GO are varied. Clusters formed by GO sheets get smaller and disperse better with increasing molecular weight of PDMS, which results in the higher critical concentration to form network (C_cr). Moreover, at GO concentration just above C_cr, the plateau modulus of samples decreases with the molecular weight of PDMS. During shear experiments, negative normal stress differences (ΔN) are observed in composites with PDMS molecular weight lower than critical entanglement molecular weight (M_c). However, positive ΔN is found in samples with PDMS molecular weight above M_c. It can be concluded that the vorticity alignment of GO clusters induces the negative ΔN based on the optical shear experiments. The possible mechanism for the positive ΔN is also proposed.     

对负离子对氧化石墨烯/聚苯胺电磁性能的影响

以过硫酸铵为引发剂,控制掺杂质子浓度为1 mol/L,分别以Cl–、CSA–(樟脑磺酸根)和SO42–为对负离子,通过原位化学氧化聚合法制备得到掺杂态氧化石墨烯/聚苯胺复合材料.采用SEM、FTIR和XRD对复合材料进行形貌和结构表征,采用四探针法、矢量网络分析仪分别测试复合材料的电磁参数,并计算材料的阻抗和反射损耗(...     

Size effects of graphene oxide on mixed matrix membranes for CO2 separation

Graphene oxide (GO)‐polyether block amide (PEBA) mixed matrix membranes were fabricated and the effects of GO lateral size on membranes morphologies, microstructures, physicochemical properties, and gas separation performances were systematically investigated. By varying the GO lateral sizes (100–200 nm, 1–2 μm, and 5–10 μm), the polymer chains mobility, as well as the length of the gas channels could be effectively manipulated. Among the as‐prepared membranes, a GO‐PEBA mixed matrix membrane (GO‐M‐PEBA) containing 0.1 wt % medium‐lateral sized (1–2 μm) GO sheets showed the highest CO₂ permeation performance (CO₂ permeability of 110 Barrer and CO₂/N₂ mixed gas selectivity of 80), which transcends the Robeson upper bound. Also, this GO‐PEBA mixed matrix membrane exhibited high stability during long‐term operation testing. Optimized by GO lateral size, the developed GO‐PEBA mixed matrix membrane shows promising potential for industrial implementation of efficient CO₂ capture. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2843–2852, 2016     

Mechanical properties of graphene oxide reinforced alumina matrix composites

Graphene oxide (GO) reinforced alumina matrix composites have been fabricated by using graphene oxide synthesized by a modified Hummer's method. Samples were prepared by powder metallurgy and consolidated by Spark Plasma Sintering (SPS). The influence of GO addition on the microstructure and mechanical properties of the composites was investigated. Results show a significant increase (almost 35%) of the fracture toughness for composites containing 0.5 wt% graphene oxide compared to sintered pure alumina. In order to find reasons for this improvement Scanning/Transmission Electron Microscopy (SEM/TEM) observations were carried out. They reveal a good interface between the reinforcement and the matrix as well as such mechanisms like branching, deflection and bridging of crack propagation.