水合肼在高岭石层间插层行为的量子化学研究

水合肼以其碱性及吸附性受到越来越多的关注,同时它在粘土中的污染问题也越来越受到重视.本工作构建了高岭石团簇模型为Al6Si6O42H42并在B3LYP/6-31G(d,p),MP2/6-31G(d,p)//B3LYP/6-31G(d,p)和MP2/6-31++G(d,p)//B3LYP/6-31G(d,p)水平下对一水合肼以及二水合肼在高岭石层间的插层性质(如:优化构型、结构参数、结合能、电荷分布、振动光谱、静电势等)进行探究.计算表明,当一水合肼进入层间后,水分子和肼分子之间的相互作用发生了改变.即水与肼分子分别以氢键的形式插层于高岭石层间,且肼与高岭石之间的相互作用要强于肼与水之间的相互作用,同时插层位点多位于高岭石四面体层和八面体层的重叠区域内,这些都是水合肼易进入高岭石层间而难以脱去的重要因素.当二水合肼进入层间后,随着层间距的不断扩大,肼分子与高岭石铝氧层之间的相互作用仍强于肼分子与水分子间的作用.但当层间距超过1.05 nm时,水分子与肼分子之间的作用则强于肼分子与高岭石的作用,这也印证了若要将肼脱附,需将层间距增大以减弱肼分子与高岭石的作用,再用溶剂将其脱附的可行性.     

高岭石插层效率评价

用基于X射线衍射分析(XRD)的插层率、基于热重分析(TGA)的热失重率和基于红外光谱分析(FTIR)的3 600 cm^-1谱带与3 700 cm^-1谱带强度比值对高岭石/二甲基亚砜(DMSO)插层复合物和高岭石/N-甲基甲酰胺(NMF)插层复合物的插层效率进行了综合评价。结果表明,当插层反应进行到1、6和25 d,高岭石/DMSO的插层率分别为5%、52%和89%;而高岭石/NMF的插层率则分别为93%、94%和95%。与此同时,高岭石/DMSO的热失重率分别为1.06%、8.06%和17.46%;而高岭石/NMF的失重率分别为6%、6.5%和14.2%。在红外光谱图中,高岭石/DMSO复合物的3 600与3 700 cm^-1带强度比分别为1.03,1.141和1.628,而高岭石/NMF复合物分别为1.403,1.433和1.612。3种评价方法显示很好的一致性,相对而言,在插层作用的初期,XRD方法比较灵敏,而在插层作用的后期,TGA和FTIR方法则显得更为灵敏和有效。     

直接置换插层法0.85 nm水合高岭石的制备

以高岭石/尿素插层复合物作为中间相,利用简单的直接置换插层法制备了d001=0.85 nm的水合高岭石。利用X射线衍射、红外光谱、扫描电镜表征处理前后高岭石结构与形貌的变化。结果表明:尿素插层后的高岭石层间距从d001=0.72 nm增大到d001=1.08 nm,经不同温度酸洗或水洗后,插层复合物转变成层间有水分子的水合高岭石(d001=0.85 nm),且高岭石晶粒厚度明显从约25 nm减小到约10 nm。在高温条件下形成的水合高岭石含量最高,90℃水洗时d001=0.85 nm水合高岭石的转化率接近70%,这种水合高岭石具有进一步的置换插层能力,是一种制备其他高岭石插层复合物很好的前驱体。与乙二醇形成d001=1.10nm乙二醇/高岭石插层复合物,其置换率达到100%。     

水分子在高岭石中插层行为的量子化学研究

采用密度泛函理论B3LYP方法,在B3LYP/6-31G(d)理论水平上,构建高岭石的层间团簇模型Si6Al6O42H42(层间距为0.844 0和1.000 0nm),并对高岭石层间及其与n(n=1～3)个水分子相互作用的团簇的各种性质进行研究,如优化的几何构型、电子密度、氢键、能量、NBO电荷分布、振动频率等.结果表明,随着水分子个数n(n=1～3)的增加,体系的能量逐渐降低.水分子通过多种类型的氢键插层于高岭石层间,其中水分子间的氢键强度最强,其次是水分子与铝氧层之间形成的氢键,再次是水分子与硅氧层之间的氢键;层间距随着插层分子的增多而增大,但高岭石层间的活性位点依然存在,且位置较插层前没有明显变化.     

高岭石/甲酰胺插层的Raman和DRIFT光谱

用Raman和漫反射红外光谱研究高岭石/甲酰胺插层反应机理及插层作用对高岭石微结构的影响.     

高岭石-硬脂酸插层复合物的制备及结构模型的提出

以张家口高岭土为原料,通过直接插层与取代相结合的方法制备高岭石-硬脂酸插层复合物。利用X射线粉末衍射、红外光谱、热重及透射电子显微镜对制备产物进行表征。结果表明:硬脂酸插入到高岭石层间,高岭石层间距d001值由0.72 nm增加到4.05~4.37 nm,插层率达到86.9%;反应时间和溶液p H值会对高岭石-硬脂酸插层复合物的层间距及插层率产生影响;甲氧基嫁接在高岭石表面,与硬脂酸分子同时存在于高岭石层间。高岭石经甲醇改性后脱羟基温度明显降低,高岭石羟基活性提高;高岭石-硬脂酸插层复合物的稳定温度在160℃以下。经过硬脂酸插层改性后的高岭石片层,从边缘开始出现卷曲现象,并且部分长条状片层形成类似埃洛石相的纳米卷;对硬脂酸插层高岭石的作用机理进行分析,结合结构计算,提出高岭石-硬脂酸插层复合物的结构模型,该模型可以解释高岭石-硬脂酸插层复合物在不同条件制备产物层间距变化的原因。     

高岭石-硬脂酸插层复合物的制备及结构模型的提出

以张家口高岭土为原料,通过直接插层与取代相结合的方法制备高岭石-硬脂酸插层复合物.利用 X射线粉末衍射、红外光谱、热重及透射电子显微镜对制备产物进行表征.结果表明:硬脂酸插入到高岭石层间,高岭石层间距d₀₀₁值由0.72 nm增加到4.05~4.37 nm,插层率达到86.9%;反应时间和溶液pH值会对高岭石-硬脂酸插层复合物的层间距及插层率产生影响;甲氧基嫁接在高岭石表面,与硬脂酸分子同时存在于高岭石层间.高岭石经甲醇改性后脱羟基温度明显降低,高岭石羟基活性提高;高岭石-硬脂酸插层复合物的稳定温度在160 ℃以下.经过硬脂酸插层改性后的高岭石片层,从边缘开始出现卷曲现象,并且部分长条状片层形成类似埃洛石相的纳米卷;对硬脂酸插层高岭石的作用机理进行分析,结合结构计算,提出高岭石-硬脂酸插层复合物的结构模型,该模型可以解释高岭石-硬脂酸插层复合物在不同条件制备产物层间距变化的原因.     

高岭石/聚丙烯酰胺插层复合物的制备与表征

The kaolinite-polyacrylamide intercalation compound was prepared first by the displacement reaction of the kaolinite-formamide intercalation precursor with 30% acrylamide ethanol solution, and then the polymerization under 140℃ for 15h with the catalysis of dibenzoyl peroxide. The XRD analyses showed that the basal spacings of kaolinite-acrylamide intercalation compound and kaolinite-polyacrylamide compound were 1.135nm and 1.144nm respectively. The kaolinite-polyacrylamide compound was able to resist to 30-min washing with water, but the kaolinite-acrylamide compound was unstable during washing. FT-IR proved that the hydrogen bonds were formed between kaolinite Si-O group and polyacrylamide NH group and between kaolinite inner surface hydroxyl and polyacrylamide C=O group, and that parts of NH group keyed into the kaolinite ditrigonal hole. TG and DTG analysis proved that kaolinite-polyacrylamide was stable under 350℃. A net weight loss of 16.63% between 370℃～500℃ is due to the removal of intercalated polyacrylamide from the interlamellar space of kaolinite. These results clearly indicate that acrylamide has been intercalated into the layers of kaolinite and was polymerized in-situ.Based on the TG data, the formula of the kaolinite-polyacrylamide intercalation compound, Al₂Si₂O₅(OH)₄?CH₂CHCONH₂?_0.736, can be calculated.     

高岭石/苯甲酰胺插层复合物的热分解行为及脱嵌反应动力学

以高岭石/二甲基亚砜为前驱体,利用置换法制备了高岭石/苯甲酰胺插层复合物。XRD和FTIR分析表明苯甲酰胺进入高岭石层间并与其形成新的氢键。采用TG、DSC研究了插层复合物的热分解行为。结果表明复合物在加热过程中发生两步分解,第一步是插层复合物的分解,即插层剂分子于231℃发生脱嵌,第二步为高岭石脱羟基的过程。针对第一阶段的脱嵌反应,采用等转化率法改进后的迭代法、Malek法以及Dollimore法等动力学方法计算得到了完整的动力学三因子:活化能Ea=75.4kJ.mol-1,指前因子A的范围为4.9×1010~8.8×1010s-1,动力学方程为:G(α)=[1-(1-α)1-n]/(1-n),f(α)=(1-α)n。     

高岭石/APTES插层复合物的表征及其脱嵌反应动力学

以高岭石/甲醇(K/M)复合物为前驱体,利用置换法制备出了高岭石/γ-氨丙基三乙氧基硅烷插层复合物(K/APTES),并应用XRD、FTIR、TEM、TG-DSC分析等表征手段对复合物进行了分析。结果表明:APTES分子的氨基与前驱体K/M的四面体硅氧烷基、嫁接在铝氧八面体表面上的甲氧基均发生键合作用形成氢键,APTES分子为两层倾斜排列于高岭石层间,倾角大小与温度有关。插层剂APTES破坏了高岭石层间的氢键,加剧了高岭石自身结构中硅氧四面体片层与铝氧八面体片层之间存在的错位,使得K/APTES插层复合物的部分片层卷曲变形。还针对复合物的插层剂APTES的脱嵌反应,采用Satava积分法和AcharBrindley-Sharp-Wendworth微分法相结合的动力学方法计算得到了完整的动力学三因子:活化能E=197.8 k J·mol-1,指前因子的对数lg(A/s-1)=14.60,最概然机理函数为:f(α)=[-ln(1-α)]-1,G(α)=α+(1-α)ln(1-α)。     

Thermal Intercalation of Alkali Halides into Kaolinite

Solid state intercalation of alkali halides into kaolinite takes place by heating pressed disks of dimethylsulfoxide (DMSO)-kaolinite complex ground in different alkali halides. This reaction involves diffusion of the DMSO outside the interlayer space and the alkali halide into the interlayer space. IR and Raman spectroscopy reveal two types of intercalation complexes: (i) almost non-hydrous, obtained during thermal treatment of the DMSO complex; and (ii) hydrated, obtained by regrinding the disk in air. The strength of the hydrogen bonds between intercalated water or halide anions and the inner surface hydroxyls decreases in the order Cl⁻>Br⁻>I⁻. Chlorides penetrate the ditrigonal holes and form hydrogen bonds with the inner OH groups. This revised version was published online in August 2006 with corrections to the Cover Date.     

高岭土／羧甲基淀粉复合颗粒的制备及其协同电流变效应

通过二次插层取代法，以二甲基亚砜为前驱体，羧甲基淀粉二次插层取代制备 了高岭土/羧甲基淀粉纳米复合材料。结合XRD，FTIR，SEM和EDS等测试手段对复合 材料的结构进行了表征。研究结果发现，羧甲基淀粉经过二次插层取代引起了高岭 土片层之间的剥离，形成剥离型纳米复合材料。该复合材料制备成电流变液出现了 较大的协同效应，具有很好的电流变行为，并发现电流变性能与复合物中羧甲基淀 粉的含量有密切关系。     

熔融插层法制备LLDPE/MgAl-LDH 剥离型纳米复合材料及其热性能研究

The interlayer surface of MgAl layered double hydroxide （MgAl-LDH） was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions （DS） to get MgAl（H-DS） LDH, and then the MgAl（H-DS） was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites. The samples were characterized by Fourier transform infrared （PTIR） spectroscopy, X-ray diffraction （XRD）, ion chromatography, transmission electron microscopy （TEM）, and thermogravimetry analysis （TGA）. The nanoscale dispersion of MgAl-LDH layers in the LLDPE matrix was verified by the disappearance of （001） XRD reflection of the modified MgAl-LDH and by the TEM observation. The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a faster charring process between 210 and 370 ℃ and a higher thermal stability above 370 ℃than LLDPE. The decomposition temperature of the nanocomposites with 10 wt% MgAl（H-DS） can be 42 ℃ higher than that of LLDPE at 40% weight loss.     

Preparation of LLDPE/MgAl-LDH Exfoliation Nanocomposites with Enhanced Thermal Properties by Melt Intercalation

The interlayer surface of MgAl layered double hydroxide(MgAl-LDH)was modified by exchanging about halfof the interlayer nitrate anions by dodecyl sulfate anions(DS)to get MgAl(H-DS)LDH,and then the MgAl(H-DS)was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites.The samples werecharacterized by Fourier transform infrared(FTIR)spectroscopy,X-ray diffraction(XRD),ion chromatography,transmission electron microscopy(TEM),and thermogravimetry analysis(TGA).The nanoscale dispersion ofMgAl-LDH layers in the LLDPE matrix was verified by the disappearance of(001)XRD reflection of the modifiedMgAl-LDH and by the TEM observation.The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a fastercharring process between 210 and 370℃ and a higher thermal stability above 370℃ than LLDPE.The decomposi-tion temperature of the nanocomposites with 10 wt% MgAl(H-DS)can be 42℃ higher than that of LLDPE at 40%weight loss.     

Highly Hydrogenated Graphene through Microwave Exfoliation of Graphite Oxide in Hydrogen Plasma: Towards Electrochemical Applications

Hydrogenated graphenes exhibit a variety of properties with potential applications in devices, ranging from a tunable band gap to fluorescence, ferromagnetism, and the storage of hydrogen. We utilize a one‐step microwave‐irradiation process in hydrogen plasma to create highly hydrogenated graphene from graphite oxides. The procedure serves the dual purposes of deoxygenation and concurrent hydrogenation of the carbon backbone. The effectiveness of the hydrogenation process is investigated on three different graphite oxides (GOs), which are synthesized by using the Staudenmaier, Hofmann, and Hummers methods. A systematic characterization of our hydrogenated graphenes is performed using UV/Vis spectroscopy, SEM, AFM, Raman spectroscopy, FTIR spectroscopy, X‐ray photoelectron spectroscopy (XPS), combustible elemental analysis, and electrical conductivity measurements. The highest hydrogenation extent is observed in hydrogenated graphene produced from the Hummers‐method GO, with a hydrogen content of 19 atomic % in the final product. In terms of the removal of oxygen groups, microwave exfoliation yields graphenes with very similar oxygen contents despite differences in their parent GOs. In addition, we examine the prospective application of hydrogenated graphenes as electrochemical transducers through a cyclic voltammetry (CV) study. The highly hydrogenated graphenes exhibit fast heterogeneous electron‐transfer rates, suggestive of their suitability for electrochemical applications in electrodes, supercapacitors, batteries, and sensors.     

超声化学法制备高岭土/二甲亚砜插层复合物的研究

采用与传统方法不同的超声化学法,用二甲亚砜(DMSO)对高岭土进行插层,大大缩短了处理时间,而且达到了较理想的插层效果。采用X -衍射研究插层间距,发现硅酸盐片层间距从0.714 nm增加至1.123 nm左右,插层率为90.9%,并对不同超声条件对插层率的影响进行了探讨。同时用FT-IR和TG/DTA等方法对插层机理进行了分析和研究。     

One Pot Synthesis of Graphene through Microwave Assisted Liquid Exfoliation of Graphite in Different Solvents

This study presents an easy and quick method for the synthesis of graphene from graphite in a set of solvents, including n-Hexadecane (n-Hexa), dimethylsulfoxide (DMSO), sodium hydroxide (NaOH), 1-octanol (OCTA), perchloric acid (PA), N,N-Dimethylformamide (DMF), ethylene glycol (EG), and ethylene diamine (ED), via microwave (MW) energy. The properties of final products were determined by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) spectroscopy, and the four-point probe technique. The XRD spectra of most of the MW-assisted graphene products showed peaks at 2θ = 26.5° and 54°. Layer numbers extend from 2 and 25, and the leading comes about were gotten by having two-layered products, named as graphene synthesized in dimethylsulfoxide (G-DMSO), graphene synthesized in ethylene glycol (G-EG), and graphene synthesized in 1-octanol (G-OCTA). G-DMF has the highest electrical conductivity with 22 S/m. The electrical conductivity is higher when the dipole moment of the used solvent is between 2 and 4 Debye (D). The FTIR spectra of most of the MW-assisted graphene products are in line with commercial graphene (CG). The UV-Vis spectra of all MW-assisted graphene products showed a peak at 223 nm referring to characteristic sp2 C=C bonds and 273 nm relating to the n → π * transition of C-O bonds.