Using Graphene Oxide to Enhance the Barrier Properties of Poly(lactic acid) Film

The ultra‐thin (polyethyleneimine/graphene oxide)_n [(PEI/GO)_n]multilayer films on poly(lactic acid) (PLA) were constructed via the layer‐by‐layer assembly. Here, the electrostatic interactions between PEI and GO were used to obtain the nanoscale composite membrane of (PEI/GO)_n on the surface of PLA film. With the number of assembling layers increased, the oxygen permeability (PO₂) of PLA film decreased substantially. As a 0.06 wt% GO solution was used with only four layers, the PO₂ decreased from 53.8 to 0.377 × 10^?4 cm³/m²/d/Pa, only 0.7% of the original PLA film. At the same time, the coated PLA film also presented a good transparency and better mechanical properties. It is a novel way to use GO on biodegradable packaging materials. Copyright © 2014 John Wiley & Sons, Ltd.     

The Effect of Thermal Reduction on the Water Vapor Permeation in Graphene Oxide Membranes

In the present study, the influence of the thermal reduction on the water vapor transmission properties of thin graphene oxide (GO) membranes is evaluated. The macroscopically measured property of the Water Vapor Transmission Rate (WVTR) exhibits step like dependence contrary to the gradual microscopic structural alterations identified by several techniques (XPS, FTIR and XRD) applied in situ during the thermal annealing process. Three distinct regions of WVTR‐values associated with distinct interlayer distances i.e., >7.5 Å, ∼6 Å and <6 Å are essentially observed which may be compared to the findings of the recently reported first principle calculations. Our experimental results enable the understanding of the water vapor unimpeded transmission through the layers of the oxygen rich GO nanostructured membranes and consequently facilitate the design of functional membranes for separation applications.     

离子化氨基酸对氧化石墨烯膜渗透汽化过程中水选择性渗透的影响

在氧化石墨烯(GO)膜通道内引入离子化基团, 可通过静电作用吸附更多的水分子, 有望实现更高效的水分子渗透。研究采用真空抽滤方法将离子化的碱性氨基酸赖氨酸(Lys)引入GO膜内, 通过共价交联制备出 Lys(Na⁺)-GO复合膜。赖氨酸分子两端的氨基与GO可交联形成C-N共价键, 从而对膜结构进行调控使其更加规整有序, 并将离子化羧酸根引入氧化石墨烯通道中。相比于未离子化的赖氨酸, 离子化的赖氨酸中荷负电的羧酸根通过静电作用提高了与水分子的作用力, 增强了膜的亲水性。通过物理结构和化学结构调控的协同作用, 面向不同的水/醇分离体系, Lys(Na⁺)-GO复合膜的渗透通量和分离因子得到同时提升。在40 ℃下, 对质量分数90%的乙醇/水、正丁醇/水以及异丙醇/水体系进行渗透汽化测试, Lys(Na⁺)(10)-GO膜(抽滤溶液中Lys(Na⁺)与GO的质量比为10)的渗透通量分别达到882、2461和1127 g/(m²·h), 渗透侧水的质量分数分别达到95.38%、99.11%和99.42%。     

氧化石墨烯改性环氧隔热涂层的耐蚀和隔热性能研究

用氧化石墨烯(GO)浓缩浆分散法制备GO改性环氧隔热涂层，在浓度(质量分数)为3.5% 的NaCl溶液(50℃)中进行腐蚀实验并测试其腐蚀前后的隔热性能。432 h的腐蚀电化学测试结果表明，用0.5%(质量分数) 的GO改性显著提高了涂层低频阻抗，涂层的耐蚀性优于无GO改性和1.0% GO改性的涂层；SEM分析结果表明，用0.5%和1.0% GO改性的隔热涂层腐蚀432 h后表面形貌完好，涂层/基体界面处没有出现裂纹和腐蚀产物，而未经GO改性的涂层出现了明显腐蚀破坏。腐蚀试验前，0.5%、1.0% GO改性的涂层与没有改性的涂层的隔热性能没有明显的区别；腐蚀432 h后涂层对250℃热源分别降温98℃、123℃、115℃，粘结强度分别降低了3.9、1.0、2.3 MPa。实验结果表明，用0.5% GO改性的涂层耐蚀和隔热性能最好。     

聚乳酸/纳米羟基磷灰石/氧化石墨烯纳米复合膜的制备及生物性能研究

采用溶液浇铸法和超声分散工艺制备了聚乳酸/纳米羟基磷灰石/氧化石墨烯(PLA/n-HA/GO)纳米生物复合膜,利用扫描电镜(SEM)对其断面形貌进行了研究,借助X射线衍射(XRD)和傅里叶变换红外光谱(FTIR)分析了纳米羟基磷灰石和氧化石墨烯的加入对所得复合膜结构的影响,并对其生物相容性进行了探讨.结果表明,氧化石墨烯和纳米羟基磷灰石在复合膜中分散均匀;细胞在复合膜上贴附牢固、铺展良好,具有良好的生长形态.聚乳酸/纳米羟基磷灰石/氧化石墨烯复合材料为细胞提供了接近天然细胞外基质的人造微环境,显示了该材料在引导组织修复和再生领域中的应用潜力.     

Film Structure of Epitaxial Graphene Oxide on SiC: Insight on the Relationship Between Interlayer Spacing,Water Content,and Intralayer Structure

Chemical oxidation of multilayer graphene grown on silicon carbide yields films exhibiting reproducible characteristics, lateral uniformity, smoothness over large areas, and manageable chemical complexity, thereby opening opportunities to accelerate both fundamental understanding and technological applications of this form of graphene oxide films. Here, we investigate the vertical inter‐layer structure of these ultra‐thin oxide films. X‐ray diffraction, atomic force microscopy, and IR experiments show that the multilayer films exhibit excellent inter‐layer registry, little amount (<10%) of intercalated water, and unexpectedly large interlayer separations of about 9.35 Å. Density functional theory calculations show that the apparent contradiction of “little water but large interlayer spacing in the graphene oxide films” can be explained by considering a multilayer film formed by carbon layers presenting, at the nanoscale, a non‐homogenous oxidation, where non‐oxidized and highly oxidized nano‐domains coexist and where a few water molecules trapped between oxidized regions of the stacked layers are sufficient to account for the observed large inter‐layer separations. This work sheds light on both the vertical and intra‐layer structure of graphene oxide films grown on silicon carbide, and more in general, it provides novel insight on the relationship between inter‐layer spacing, water content, and structure of graphene/graphite oxide materials.     

Effects of Pb Intercalation on the Structural and Electronic Properties of Epitaxial Graphene on SiC

The effects of Pb intercalation on the structural and electronic properties of epitaxial single‐layer graphene grown on SiC(0001) substrate are investigated using scanning tunneling microscopy (STM), noncontact atomic force microscopy, Kelvin probe force microscopy (KPFM), X‐ray photoelectron spectroscopy, and angle‐resolved photoemission spectroscopy (ARPES) methods. The STM results show the formation of an ordered moiré superstructure pattern induced by Pb atom intercalation underneath the graphene layer. ARPES measurements reveal the presence of two additional linearly dispersing π‐bands, providing evidence for the decoupling of the buffer layer from the underlying SiC substrate. Upon Pb intercalation, the Si 2p core level spectra show a signature for the existence of Pb? Si chemical bonds at the interface region, as manifested in a shift of 1.2 eV of the bulk SiC component toward lower binding energies. The Pb intercalation gives rise to hole‐doping of graphene and results in a shift of the Dirac point energy by about 0.1 eV above the Fermi level, as revealed by the ARPES measurements. The KPFM experiments have shown that decoupling of the graphene layer by Pb intercalation is accompanied by a work function increase. The observed increase in the work function is attributed to the suppression of the electron transfer from the SiC substrate to the graphene layer. The Pb intercalated structure is found to be stable in ambient conditions and at high temperatures up to 1250 °C. These results demonstrate that the construction of a graphene‐capped Pb/SiC system offers a possibility of tuning the graphene electronic properties and exploring intriguing physical properties such as superconductivity and spintronics.     

高纯粉状钨酸的某些理化特性研究

用“氨净化-络合制浆-酸分解法”制备高纯粉状钨酸,并对这种钨酸的某些理化特性进行了试验研究,结果发现用该工艺制得的钨酸不但纯度高(≥99.99％),而且颗粒比一般工业钨酸更细(平均粒度0.59μm),具有良好的化学活性。分子内不含结晶水是沉淀疏松,不发粘,易于过滤,洗涤的重要原因。同时试验结果还表明,钨酸(或APT)中微量杂质对W-Re合金粉末的理化性能有一定影响。     

不同浓度盐酸刻蚀对钛基锡锑钌氧化物涂层电极活性和寿命的影响

钛基体的酸刻蚀是钛基氧化物涂层电极能否在湿法冶金中应用的关键前处理步骤。采用不同质量分数(5%,10%,15%,20%,25%)的盐酸溶液刻蚀钛基体并制备钛基锡锑钌氧化物涂层电极。通过扫描电镜、电化学工作站及加速腐蚀测试对电极的表面形貌、电催化活性及强化寿命进行了表征,以获得钛基体刻蚀的最佳盐酸浓度。结果表明:随着盐酸浓度升高,钛基体表面腐蚀的程度加深,孔径变大,从纳米级至数微米,扩孔腐蚀起主导作用;随着盐酸浓度的升高,刻蚀后制备的涂层电极的析氧过电位和电荷传递电阻先减小后增大,伏安电量先增大后降低;当盐酸浓度为20%时,刻蚀后制备的涂层电极的析氧过电位最低,其值为274.6 m V(500 A/m^2),电荷传递电阻最低,为0.216 5Ω·cm^2,伏安电量最高,达0.029 9 C/cm^2;在150 g/L H2SO4溶液中以1 A/cm^2的电流密度条件进行加速寿命试验结果显示,浓度为20%的盐酸刻蚀后制备的电极具有最长的使用寿命,其电极寿命为80 h,是浓度为5%的盐酸刻蚀后制备的电极寿命的2.85倍。     

Exploring the Nickel–Graphene Nanocomposite Coatings for Superior Corrosion Resistance: Manipulating the Effect of Deposition Current Density on its Morphology,Mechanical Properties,and Erosion‐Corrosion Performance

The use of graphene‐based composite as anti‐corrosion and protective coatings for metallic materials is still a provocative topic worthy of debate. Nickel–graphene nanocomposite coatings have been successfully fabricated onto the mild steel by electrochemical co‐deposition technique. This research demonstrates the properties of nickel–graphene composite coatings influenced by different electrodeposition current densities. The effect of deposition current density on the; surface morphologies, composition, microstructures, grain sizes, mechanical, and electrochemical properties of the composite coatings are executed. The coarseness of deposited coatings increases with the increasing of deposition current density. The carbon content in the composite coatings increases first and then decreases by further increasing of current density. The improved mechanical properties and superior anti‐corrosion performance of composite coatings are obtained at the peak value of current density of 9 A dm^?2. The incorporation of graphene sheets into nickel metal matrix lead to enhance the micro hardness, surface roughness, and adhesion strength of produced composite coatings. Furthermore, the presence of graphene in composite coating exhibits the reduced grain sizes and the enhanced erosion–corrosion resistance properties.