以MTES为硅源制备透明可压缩的甲基倍半硅氧烷气凝胶及其表征

目前利用甲基三乙氧基硅烷制备的气凝胶主要是以甲醇或乙醇为溶剂,存在制备成本高、气凝胶隔热性能和透明度差的问题。为了对该气凝胶制备工艺和性能进行实质性改进,本文以水溶剂代替醇类溶剂,利用表面活性剂的增容作用,结合溶胶-凝胶酸碱两步法以及CO₂超临界干燥法制备得到了具有高透明度的超疏水可压缩的甲基倍半硅氧烷气凝胶,并且对三官能团硅源含量变化影响表面活性剂十六烷基三甲基溴化铵分子行为的内容进行了对比分析。结果表明：在水溶剂体系中,三官能团硅源含量的增加会影响表面活性剂胶束的形态,从而促使气凝胶的骨架结构逐渐由均匀分布的纤维状转变为密集堆积的颗粒状。在对置换工艺的研究中,发现用强碱性水溶液替代传统水溶液作为置换液时会有更加高效的置换效率,使得孔隙中杂质残留较少,以致0～300℃热重分析过程中几乎没有质量损失。该气凝胶可以广泛应用于建筑物的隔热墙和窗户的保温层。     

以线性酚醛树脂为炭前驱体制备有序介孔炭及其表征

以三嵌段共聚物F127和P123为模板剂,线性酚醛树脂(PF)为炭前驱体,利用有机-有机自组装制备了具有二维六方结构和蠕虫结构的介孔炭.采用XRD、TEM、N2吸附/脱附等方法对介孔炭的结构进行了表征,研究了模板剂用量和模板剂类型对上述介孔炭结构的影响.结果表明:当模板剂F127与PF的质量比由1:2变为1:1时,所得介孔炭的孔壁厚度有所下降,但比表面积、孔容和孔径分别从576 m2·g-1、0.29 cm3·g-1和2.7 nm提高到670m2·g-1、0.40 cm3· g-1和3.2 nm;分别以F127和P123为模板剂制备的介孔炭F-1-500和P-1-500的孔径大小基本相同,但P-1-500的孔壁厚度相对于F-1-500降低了37.4％,且有序性下降,仅能得到蠕虫状结构.     

磷掺杂石墨烯的制备与表征

以氧化石墨烯和三苯基磷为前驱体,利用高温热处理方法制备磷掺杂石墨烯。采用X射线衍射、扫描电镜、透射电镜、选区电子衍射、能量色散谱和X射线光电子能谱对石墨烯的形貌、结构和组成进行表征。结果表明,氧化石墨烯在热处理过程中实现原位还原和磷掺杂,合成的磷掺杂石墨烯呈透明褶皱状,含有2~5层石墨层,磷元素以P-C和P-O构型掺杂进石墨烯晶格中。通过控制反应温度可调控产物中磷元素的含量和化学态分布。     

Preparation and characterization of aluminum hypophosphite/reduced graphene oxide hybrid material as a flame retardant additive for PBT

Aluminum hypophosphite/reduced graphene oxide (AHP/RGO) hybrid flame retardant with high thermal stability was successfully prepared by a one‐step method consisting of the simultaneous reduction of graphene oxide and the deposition of AHP on graphene. The as‐prepared sample was characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X‐ray photoelectron spectroscopy. The obtained sample was used as a flame retardant for polybutylene terephthalate, and the flame retardancy of the composites was investigated by a limiting oxygen index test, a UL‐94 test, and cone calorimetry. The results showed that AHP/RGO exhibited improved flame retardancy when compared with bare AHP. The addition of AHP/RGO to polybutylene terephthalate led to a significant reduction in the heat release rate and resulted in excellent anti‐dripping properties for the composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and supercapacitor performance studies of N-doped graphene materials using o-phenylenediamine as the double-N precursor

N-doped graphene (NG) materials have been prepared through a one-step solvothermal reaction by using o-phenylenediamine as a double-N precursor. N-doping and reduction of graphene oxide (GO) are both achieved simultaneously during the solvothermal reaction. The results of scanning electron microscopy and high resolution transmission electron microscopy measurements indicate that NG is highly crumpled. And the N-doping is confirmed by elemental analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transformed infrared spectroscopy and ultraviolet–visible spectroscopy. The doping level of nitrogen reaches up to 7.7 atom% and the types in NG are benzimidazole-N and phenazine-N. The NG materials exhibit excellent electrochemical performance for symmetric supercapacitors with a high specific capacitance of 301 F g⁻¹ at a current density of 0.1 A g⁻¹ in 6 M KOH electrolyte, which is remarkably higher than the solvothermal products of pristine GO (210 F g⁻¹ at 0.1 A g⁻¹). The NG materials also exhibit superior cycling stability (97.1% retention) and coulombic efficiency (99.2%) after 4000 cycles, due to the high content of nitrogen atoms, unique types of nitrogen and improved electronic conductivity.     

氧化石墨烯-壳聚糖-聚乙二醇纳米复合物的制备及表征

针对纳米氧化石墨烯(NGO)在生理溶液中易聚集沉淀的问题,文中将壳聚糖-聚乙二醇接枝聚合物通过缩合反应与NGO共价连接,得到氧化石墨烯-壳聚糖-聚乙二醇(NGO-CS-PEG)纳米复合物。采用FTIR,SEM,DLS等方法对复合物进行表征。在FTIR图谱中,1776,1480 cm-1处同时出现酰胺键特征吸收峰,表明NGO-CS-PEG的成功制备。SEM表征结果显示复合物具有良好的单片层结构。DLS测定结果显示NGO-CS-PEG的平均粒径为282.5 nm,PDI为0.287。以PBS(p H=7.4)及DMEM细胞培养液为模拟生理溶液,纳米复合物在30 d范围内均能在溶液中稳定分散,未出现聚集沉淀现象。研究表明制备的NGO-CS-PEG纳米复合物粒径分布均匀、片层形貌良好、在生理溶液中分散稳定,为其在生物医药领域中的应用奠定了基础。     

Synthesis and characterization of mesostructured tungsten nitride by using tungstic acid as the precursor

Mesostructured tungsten nitride was firstly prepared from tungstic acid via the temperature programmed reaction with ammonia. The N₂ adsorption isotherm of as-synthesized tungsten nitride was of type IV with a type H-3 hysteresis loop. BJH pore size distribution was of bimodal distribution (2.5 and 3.5 nm), among which the latter was the main channel of tungsten nitride. The surface area of as-synthesized tungsten nitride was up to 89 m² g⁻¹. XRD pattern showed that the crystal phase of the product was β-W₂N. The effect of synthesis parameters on the surface area of tungsten nitride was investigated extensively. The nitridation mechanism was investigated by in-situ XRD and N₂ adsorption analysis. It was found that H₂WO₄ was initially transformed into WO₃ by eliminating the axial water molecules, and WO₃ retained the layered and porous structure of H₂WO₄. Below 773 K, WO₃ was just partially reduced to W₂₀O₅₈ and W₂₀O₄₀. Above 773 K, β-W₂N phase could be detected. It indicated that during nitridation, WO₃ was gradually reduced and then the homogeneous substitution of oxygen vacancies in the reduced oxides with nitrogen atoms occurred. Based on the experimental results, a reduction-nitridation mechanism was firstly proposed.     

Preparation and characterization of graphene oxide reinforced PVA film with boric acid as crosslinker

PVA films were prepared through aqueous solution method, and boric acid (BA) as well as graphene oxide (GO) was added to improve the mechanical and thermal properties. It was found that 5 wt % BA could increase the tensile strength threefold (from 23.3 to 67.7 MPa), and the incorporation of 0.2 wt % GO would provide additional percentage growth of 30% (from 67.7 to 88.5 MPa). Moreover, an enhancement of thermal stability of PVA film was found when BA or GO filler was added. The reinforcement mechanisms of both BA and GO were investigated, and a competitive phenomenon that the addition of BA would influence the reinforcement effect of GO sheets was found. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42000.     

Preparation and characterization of graphene composites with conducting polymers

We report a new route for preparing electro‐conductive composites based on reduced graphene oxide (RG‐O) and poly(3,4‐ethylenedioxythiophene) (PEDOT). The composites were prepared by in situ polymerization of EDOT in aqueous mixture containing RG‐O platelets modified with poly(sodium 4‐styrenesulfonate) (PSS). In the synthetic process, PSS molecules stabilize RG‐O in the aqueous phase and function as a polymerization template to hybridize PEDOT chains along RG‐O platelets. Compared with the RG‐O platelets, the resulting composites show an enhanced electrical conductivity of 9.2 S cm^?1 with good thermal stability. Copyright © 2011 Society of Chemical Industry     

Preparation and characterization of graphene reinforced PA6 fiber

Here, we report the successful preparation of PA6/GO composite fibers through in situ polymerization and the melting spinning method. The results suggest that graphene has induced only minor changes on the relative viscosity yet exhibits significant effects on the crystallization characteristics. The SEM images of the fibers have shown several expended borders as a consequence of graphene addition. The maximum strength of the composite fibers (5.3 cN/dtex) has been reached 0.05 wt % graphene added to the system; the draw ratio was equaled to 3.8. Compared to the neat PA6 fiber, the fibers with graphene displayed superior creep resistance features; the creep rate constant was 0.38 at a 0.05 graphene concentration, with a draw ratio of 3.5. The approach employed in this research paves the way towards PA6/graphene nanocomposites have been prepared through in situ polymerization using caprolactam and graphene oxide/water pulp as starting materials. In situ polymerization approach facilitated a superior interaction between PA6 and graphene. Compared to graphene oxide powder, the graphene oxide in water pulp has prevented the agglomeration when added to the caprolactam melt, leading to its enhanced dispersion within the system. PA6/graphene as‐spun fiber has been produced by the mean of melt‐spinning strategy using a melt‐spinning machine, obtaining products with different draw ratios after drawing at 120 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45834.     

植物油型防结块剂的制备条件研究

以植物油、非铵盐类表面活性剂为原料,制得一种环境友好型防结块剂,通过模拟堆压加速结块法对施用该防结块剂复混肥的防结块效果进行了测定。结果表明,当m(防结块剂)∶m(复混肥)=5∶1 000,防结块剂组成为m(聚乙二醇2000+聚二甲基硅氧烷)∶m(聚山梨酯B)=1∶2且m(复配表面活性剂)∶m(植物油)=1∶100时,复混肥的最小结块率可达到9.0%,优于机油-胺类防结块剂。     

Preparation and characterization of magnetite/dextran nanocomposite used as a precursor of magnetic fluid

Magnetic nanoparticles were synthesized by the co-precipitation of Fe²⁺ and Fe³⁺ using ammonium hydroxide (NH₄OH). The obtained nanoparticles were characterized by X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer. In order to prepare a biocompatible water-based magnetic fluid, the nanoparticles were modified by dextran through a two-step method. The influences of dextran molecular weight on the size, morphology, coating efficiency and magnetic property of magnetite/dextran nanocomposite were investigated. The magnetite/dextran nanocomposite was dispersed in water to form a magnetic fluid by ball milling. The rheological property of magnetic fluids was investigated using a rotating rheometer.     

Preparation and electrochemical characterization of MnOOH nanowire–graphene oxide

MnOOH nanowire–graphene oxide composites are prepared by hydrothermal reaction in distilled water or 5% ammonia aqueous solution at 130 °C with MnO₂–graphene oxide composites which are synthesized by a redox reaction between KMnO₄ and graphene oxide. Powder X-ray diffraction (XRD) analyses and energy dispersive X-ray analyses (EDAX) show MnO₂ is deoxidized to MnOOH on graphene oxide through hydrothermal reaction without any extra reductants. The electrochemical capacitance of MnOOH nanowire–graphene oxide composites prepared in 5% ammonia aqueous solution is 76 F g⁻¹ at current density of 0.1 A g⁻¹. Moreover, electrochemical impedance spectroscopy (EIS) suggests the electrochemical resistance of MnOOH nanowire–graphene oxide composites is reduced when hydrothermal reaction is conducted in ammonia aqueous solution. The relationship between the electrochemical capacitance and the structure of MnOOH nanowire–graphene oxide composites is characterized by cyclic voltammetry (CV) and field emission scanning electron microscopy (FESEM). The results indicate the electrochemical performance of MnOOH nanowire–graphene oxide composites strongly depends on their morphology.     

Preparation and characterization of graphene paper for electromagnetic interference shielding

Syntheses of multifunctional structures, both in two-dimensional and three-dimensional space, are essential for advanced graphene applications. A variety of graphene-based materials has been reported in recent years, but combining their excellent mechanical and electrical properties in a bulk form has not been entirely achieved. Here, we report the creation of novel graphene structures such as graphene pellet and graphene paper. Graphene pellet is synthesized by chemical vapor deposition (CVD), using inexpensive nickel powder as a catalyst. Graphene pellet can be further processed into a graphene paper by pressing. The latter possesses high electrical conductivity of up to 1136 ± 32 S cm⁻¹ and exhibits a breaking stress at 22 ± 1.4 MPa. Further, this paper-like material with thickness of 50 μm revealed 60 dB electromagnetic interference (EMI) shielding effectiveness.     

Synthesis, characterization and optical limiting property of covalently oligothiophene-functionalized graphene material

An organic solution-processable functionalized graphene hybrid material with oligothiophene (6THIOP-NH-SPFGraphene) has been synthesized. The thermogravimetry analysis data shows that the hybrid is more stable than its parent graphene oxide as observed with an increased onset temperature. Ultraviolet-visible absorption and fluorescence emission data show that the attachment of the electron-acceptor group (graphene oxide sheet) onto the oligothiophene molecules results in an improved absorption than its parent compound in the whole spectral region and an efficient quenching of photoluminescence. The optical limiting properties were studied by using the open-aperture Z-scan measures at 532 nm, and the results show that 6THIOP-NH-SPFGraphene demonstrated a superior optical limiting effect, better than that of the benchmark optical limiting material C₆₀.     

以水玻璃为硅源喷雾干燥制备SiC前驱体

以廉价的水玻璃和炭黑为原料,通过制备均匀混合的前驱体,利用碳热还原反应合成出超细SiC粉体。比较研究了前驱体喷雾干燥与搅拌干燥两种制备方法对体系碳热还原反应的影响,重点考察了喷雾干燥制备过程中主要工艺参数对前驱粉体密度及收率的影响。结果表明:喷雾制备的前驱体具有更高的反应活性,在1550℃下反应2h就可使SiO2转化率达到89.4%,搅拌干燥制备的前驱体转化率只有65.2%。喷雾干燥过程中,适当提高进口温度、喷雾头转速并降低料液的固体含量,可获得高收率、高产率的前驱粉体,利于整个制备工艺生产效率及产率的提高。     

热塑性聚氨酯/石墨烯改性聚氨酯注浆材料的制备与性能研究

采用石墨烯、热塑性聚氨酯（TPU）复合改性聚氨酯注浆材料,并添加少量的粉煤灰、炉底渣及碱性激发剂制备一种低密度、高强度、快硬性的TPU/石墨烯改性聚氨酯注浆材料。借助聚氨酯弹性体材料密度测试仪、万能材料试验机、渗透系数测试仪、荧光显微镜对TPU/石墨烯改性聚氨酯注浆材料的密度、膨胀倍数、抗压强度、阻燃性能、渗透系数及微观形貌进行表征,深入分析了石墨烯和TPU的种类和含量对聚氨酯注浆材料基本物理性能、力学性能及微观结构的影响。结果表明,TPU/石墨烯改性聚氨酯注浆材料的密度为0.24~1.25 g/cm³,膨胀倍数最高可达38倍,抗压强度为15.0~43.8 MPa,相比普通聚氨酯注浆材料,改性聚氨酯注浆材料抗压强度提升1倍以上。酒精灯燃烧试验显示注浆材料无焰燃烧时间均小于20 s。石墨烯和TPU均可提高聚氨酯的强度和耐久性,改善TPU的微观形貌。TPU/石墨烯改性聚氨酯注浆材料表现出良好的强度、耐久性及弹性,是一种性能优异的注浆材料。