静电纺丝法制备PVA-SA-CuTsPc纳米纤维改性CMC-PVA/CS-PVA双极膜

分别用Fe3+离子和戊二醛作为交联剂对羧甲基纤维素钠(CMC)-聚乙烯醇(PVA)阳膜层和壳聚糖(CS)-聚乙烯醇阴膜层进行改性,利用静电纺丝法制备聚乙烯醇(PVA)-海藻酸钠(SA)-四磺酸基铜酞菁(CuTsPc)纳米纤维纺丝,引入中间界面层,制备CMC-PVA/PVA-SA-CuTsPc/CS-PVA双极膜(BPM),并用扫描电镜、接触角测定仪,电流密度-槽电压关系曲线、交流阻抗谱等对制备的双极膜进行了表征。研究结果表明,经PVA-SA-CuTsPc纳米纤维纺丝改性后,CMC-PVA阳膜表面亲水性增强,双极膜的中间界面层水解离效率提高,膜阻抗和槽电压下降。当电流密度为90 mA/cm2时,CMC-PVA/PVA-SA-CuTsPc/CS-PVA(w(CuTsPc)=3.0%)双极膜的电阻压降(即膜IR降)仅为0.5 V。     

掺杂无机纳米材料光催化双极膜的制备与表征

将柔性链聚乙烯醇(PVA)分别与刚性链天然高分子海藻酸钠(SA)和壳聚糖(CS)共混,以增强其柔韧性及双极膜界面层的相容性。然后分别以纳米无机半导体材料和戊二醛为交联剂,对PVA/SA和PVA/CS进行改性,制备了PVA-mSA/mCS双极膜。测定了双极膜的J-V曲线、膜阻抗、接触角和溶胀度。以扫描电镜对PVA-ZnO-SA/mCS膜成分与形貌作表征,膜厚约121μm,中间界面层厚约5μm。电子能谱图表明氧化锌均匀分布在阳膜层中。实验结果表明,采用纳米ZnO改性后双极膜的亲水性增强,具有更强的中间界面层水解离能力,较小的工作电压和较低的膜阻抗,可以广泛应用于绿色化学和环境治理。     

双极膜中间界面层研究进展

以双极膜为基础的水解离技术有广泛的应用 ,同时双极膜还可以用作膜反应器以及生物膜模型 .在这些应用中 ,双极膜的中间界面层起到了根本性的作用 ,因此研究双极膜的中间界面层具有重要的意义 .总结了中间界面层的各种属性 ,从这些属性可以看出它的特殊性 ,并讨论了中间界面层的物质构成 ,为双极膜的改性提供了参考     

以络合金属作催化剂的双极膜制备及电学性能

基于国内尚没有市售的良好双极膜,本研究以氯甲基化聚砜和磺化聚苯醚作为双极膜的阴阳膜层,在双极膜中间界面层固定络合金属作为催化剂,分别利用SnSO4、CrCl3、NiSO4作为催化剂制得3种双极膜,并与不添加任何催化剂制得的双极膜进行了比较.实验表明,络合金属对双极膜水解离有很好的催化作用,当中间界面层含有络合金属催化剂时,双极膜的水解离电势大大降低,并得到3种络合金属的催化活性为:Cr3+>Ni2+>Sn2+;过多催化剂用量会使双极膜的膜电阻增加;络合金属催化剂对双极膜的选择透过度影响不大,可以忽略;双极膜中间界面层中的络合金属催化剂与阴阳膜面的附着力不强,在酸碱环境中有些出现脱落或溶解.     

PAAS-CMC/Mel-CS双极膜的制备及性能

分别以聚丙烯酸钠(PAAS)和Cr3+改性羧甲基纤维素钠(CMC)阳离子交换膜层,以三聚氰胺(Melamine)和戊二醛改性壳聚糖阴离子交换膜层(CS)制得PAAS-CMC/Mel-CS双极膜(BPM).该双极膜具有较高的离子交换容量、离子渗透性,较低的交流阻抗和工作电压.以该双极膜组装的电槽电压明显低于未经改性的mCMC/mCS BPM膜电槽.当阴阳两膜层中添加的PAAS和质量分数为8.0％的三聚氰胺,工作电流密度达80 mA/cm2时,电槽的工作电压仍小于5.3V.     

高强度超拉伸全物理交联双网络水凝胶的制备与性能

以锂藻土(Laponite)与聚丙烯酰胺(PAM)间的氢键交联作用网络形成第1网络、以三价铁离子(Fe~(3+))与海藻酸钠(Alginate)间的离子交联作用形成第2网络,制备了锂藻土-聚丙烯酰胺/Fe~(3+)-海藻酸钠(Laponite-PAM/Fe~(3+)-Alginate)全物理交联双网络水凝胶。通过扫描电镜表征了Laponite-PAM/Fe~(3+)-Alginate双网络水凝胶的微观结构,探究了Fe~(3+)浓度和锂藻土含量对Laponite-PAM/Fe~(3+)-Alginate双网络水凝胶力学性能的影响,并通过拉伸-回复测试表征了水凝胶的回复性能和抗疲劳性能。结果表明,Laponite-PAM/Fe~(3+)-Alginate全物理交联双网络水凝胶内部具有致密的三维网络结构,其断裂强度可达2.4 MPa,断裂伸长率可达2600%,韧性可达44.8 MJ/m~3,具有优异的力学性能、良好的回复性能及抗疲劳性能。     

固定基团种类对双极膜性能的影响

聚苯醚溴化制备溴化聚苯醚(BPP0),与不同的胺反应引进不同的官能团制备阴膜层,再通过溶剂浇铸的方法涂磺化聚苯醚溶液制备双极膜.结果表明,不同固定基团双极膜的水解离性能与形成阴膜层基团的叔胺的pKb值有直接的关联:随着形成功能基团叔胺pKa值的增加,双极膜的催化水解离能力下降.同时研究了不同基团双极膜在不同电流密度下水解离时酸隔室的pH变化,尽管所考察的基团均有一定的水解离作用,但从实际的应用效果来看,有些基团如三丙胺和三丁胺等形成的季铵基团,由于亲水性的局限并不适合于用作双极膜阴膜层的固定基团.     

碳纳米管对PP/SPTW复合材料力学性能的影响

目的研究不同含量的多壁碳纳米管(CNT)对聚丙烯/六钛酸钾晶须复合材料力学性能的影响。方法将经表面改性处理的多壁碳纳米管与改性过的六钛酸钾晶须、聚丙烯(PP)、马来酸酐接枝聚丙烯(PP-g-MAH),采用熔融共混法,利用双辊开炼机熔融共混制得PP/PP-g-MAH/SPTW/碳纳米管复合材料。比较不同含量的改性多壁碳纳米管对PP/PP-g-MAH/SPTW复合材料力学性能的影响。结果多壁碳纳米管表面经过混酸处理后,在复合材料中分散均匀,与聚合物基体界面间结合良好,对复合材料起到增韧增强作用,但是当碳纳米管质量分数较大时,开始出现团聚现象,反而使复合材料的力学性能降低。结论当碳纳米的质量分数为0.5%左右时,复合材料力学性能最佳。     

改性碳纳米管处理碳纤维的效果表征

采用浓硫酸/浓硝酸氧化处理多壁碳纳米管(MWCNTs),再将氧化后的碳纳米管与硅烷偶联剂(KH560)进行接枝,制备了硅烷偶联剂表面化学修饰的MWCNTs。在此基础上,将改性前后的碳纳米管分散在环氧树脂体系中,涂覆处理碳纤维。研究处理前后碳纤维力学性能和界面性能的变化。通过红外光谱(FTIR)和透射电镜(TEM)分析,表明KH560已成功接枝到多壁碳纳米管上;通过分散性实验证明了改性后的碳纳米管分散性提高;对处理后的碳纤维进行力学性能测试,并用扫描电镜(SEM)观察分析断面形态变化,结果表明,当碳纳米管的含量为0.5%时,改性碳纳米管处理的碳纤维拉伸强度和拉伸模量分别提高23.83%和7.11%,界面性能增强。     

二茂铁改性双极膜技术制备3-甲基-2-吡啶甲酰胺

以二茂铁作为交联催化中心对海藻酸钠阳膜进行改性,制备了mSA-mCS聚合物双极膜.测定了双极膜的红外光谱、海藻酸钠(SA)和壳聚糖(CS)电荷密度、OH-渗透性、I-V工作曲线及交流阻抗.OH-渗透性和膜交流阻抗的测试结果表明,mSA-mCS双极膜经二茂铁离子改性后,双极膜中间层中水解离的性能得到了提高,同时降低了膜阻...     

Basalt fiber–epoxy laminates with functionalized multi-walled carbon nanotubes

Cross-ply laminates reinforced with basalt fibers and functionalized multi-walled carbon nanotubes (MWCNTs) were fabricated from unidirectional epoxy prepregs. MWCNTs with varied surface conditions were prepared by oxidization or esterification, and then dispersed into a DGEBA epoxy system. The dispersion of the MWCNTs in the epoxy was improved by surface modification, resulting in improved composite mechanical properties as well. Significant increases in elastic modulus and strength were observed for epoxies with functionalized MWCNTs, especially for esterified species. When MWCNT – filled epoxies were used as matrices for basalt fiber/epoxy laminates, however, the reinforcement effects of MWCNTs on the composite elastic modulus exceeded micromechanics based semi-empirical predictions and were independent of surface functionalization. SEM morphological observations and the results of the micromechanical model revealed that nanotube re-distribution and orientation during processing was responsible for the enhancement of fiber-dominated mechanical properties. This work demonstrated the feasibility of in situ alignment and dispersion of functionalized nanotubes in multi-scale composite laminates.     

Surfactant assisted dispersion of functionalized multi-walled carbon nanotubes in aqueous media

The dispersibility of unfunctionalized and three differently functionalized multi-walled carbon nanotubes (MWNTs) in the presence of anionic, cationic, and non-ionic surfactants was investigated. Significant differences in their dispersibility were revealed by UV–vis spectroscopy of the dispersed MWNTs. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, streaming potential measurements as well as pH measurements were conducted to characterize the MWNTs and their dispersions. Based on this information, possible interaction mechanisms between the surfactants and the differently functionalized MWNTs are proposed in order to account for the distinct dispersibility observed. Aqueous sizings containing low weight fractions of MWNTs were used for on-line modification of glass fibre (GF) sizings and preparation of GF/polypropylene composites, resulting in enhanced mechanical properties.     

Concise route to styryl-modified multi-walled carbon nanotubes for polystyrene matrix and enhanced mechanical properties and thermal stability of composite

Effective functionalization of multi-walled carbon nanotubes (MWCNTs) with styryl group was carried out via the esterification reaction of the carboxylate salt of carbon nanotubes and 4-vinylbenzyl chlorides in toluene. The functionalized MWCNTs were characterized through FTIR and Raman spectra to confirm the styryl groups covalently connected to the surface of MWCNTs. The weight loss of functionalized moieties determined by thermogravimetry-differential scanning calorimertry analysis is around 36%. Nanotube-reinforced polystyrene were fabricated by mixing functionalized MWCNTs and polystyrene. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the functionalized nanotubes had a better dispersion than the unfunctionalized MWCNTs in the matrix. Moreover, styryl-modified MWCNTs/PS nanocompsite presented obvious improvements in mechanical properties and thermal stability.     

Effects of carbon nanotube functionalization and annealing on crystallization and mechanical properties of melt-spun carbon nanotubes/poly(ethylene terephthalate) fibers

To generate poly(ethylene terephthalate) (PET) fibers with enhanced mechanical properties, we prepared melt-spun PET fibers that incorporated pristine, acid-treated, and functionalized multi-walled carbon nanotubes (MWNTs) with 2-phenylethyl alcohol and 4-phenyl-1-butanol. The incorporation of MWNTs into the melt-spun fibers resulted in increased crystallization of PET but lower breaking stress than that of pure PET fibers, even in those containing well-dispersed functionalized MWNTs. The breaking stress of drawn composite fibers was also lower than that of pure PET fibers prepared at the same draw ratio. However, the annealing of melt-spun fibers enhanced the mechanical properties and crystallization, and the annealing effect was more dominant for composite fibers with functionalized MWNTs. These findings indicate that the presence of well-dispersed MWNTs disturbs the crystallization and orientation of PET molecules in highly stressed fibers, which differs from MWNT-induced crystallization of PET molecules in relaxed fibers.     

Modification of multi-walled carbon nanotubes by Diels-Alder and Sandmeyer reactions

Random (L) and aligned (A) multi-walled carbon nanotubes (MWNTs) were modified by Diels-Alder (DA) [4+2] cycloaddition, Sandmeyer (SM) reaction and by catalytic oxidation (OX). The properties of modified carbon nanotubes were studied by dispersability tests, elemental analysis, thermogravimetry/mass spectrometry, X-ray photoelectron spectroscopy, and NMR spectroscopy. The cycloaddition reaction could only be successfully performed with the L-MWNTs in molten and in solution state by using an aluminum chloride homogeneous catalyst. The efficiency and thermal stability of the solution phase cycloaddition were much higher than in the case of modification in the molten phase. The functionalization of both types of MWNTs by Sandmeyer reaction was carried out by copper(I) and iron(ll) ions that helped in the radical decomposition of diazonium salts. Successful functionalization of nanotubes is achieved by a long decomposition time of the thermally activated diazonium salts. To the contrary, in the case of radical decomposition of diazonium salts, the time is not a decisive parameter. The dispersability tests have proved the changes in the physical features of modified carbon nanotubes depending on the hydrophobic and hydrophilic character of the solvents. The presence of the modifying groups and their fragments from the functionalized MWNTs has been demonstrated by thermogravimetry/mass spectrometry (TG/MS). Relatively high concentration of sulfur atoms was detected by X-ray photoelectron spectroscopy in nanotubes modified by sulfur substituent groups. In the case of catalytic oxidation, the X-ray photoelectron spectroscopic signal of oxygen bound to nanotubes showed considerable change as compared to pristine nanotubes. Due to the high thermal stability of modified multi-walled carbon nanotubes, the functionalized derivatives are applicable in several industrial fields.     

Functionalization of multi-walled carbon nanotubes with bis(2,2':6',2"-terpyridine) ruthenium(II)-connected diblock polymer

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a bis(2,2':6',2"-terpyridine) ruthenium(ll)-connected diblock poly(N-isopropyacryamide) (RuTpyPNIPAM) by a simple methodology of covalent amidation. The composition and structure of the functionalized ruthenium multi-walled carbon nanotubes (RuMWCNTs) were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscopy (SEM). These characterization methods confirm that after functionalization, ruthenium metallopolymer are interconnected or attached as aggregated structures on the surface of the carbon nanotubes.     

Poly(adipic acid-hexamethylene diamine)-functionalized multi-walled carbon nanotube nanocomposites

Poly(adipic acid-hexamethylene diamine) (PA66)-functionalized multi-walled carbon nanotubes (PACNT) were fabricated using amino multi-walled carbon nanotubes (AMWNT), adipic acid-hexamethylene diamine salt as reactants at 260–270 °C. The solubility of AMWNT in formic acid is improved after PA66 functionalization. PA66 was successfully grafted onto the surface of AMWNT to form a core–shell nanostructure. AMWNT are surrounded by PA66 chains with an average thickness of 3 nm. The length of PA66 chains on the surface of AMWNT decreases, with the content of AMWNT increasing. The thermal decomposition temperature of the composite is lower than that of PA66 functionalized carboxylic multi-walled carbon nanotubes. The storage modulus of PACNT containing 5 wt% AMWNT is 2.8-fold that of PA66; and it increases as the content of AMWNT increases.     

Electrical and optical properties of reduced graphene oxide and multi-walled carbon nanotubes based nanocomposites: A comparative study

Graphene and multi-walled carbon nanotubes have attracted interest for a number of potential applications. One of the most actively pursued applications uses graphene and carbon nanotubes as a transparent conducting electrode in solar cells, displays or touch screens. In this work, in situ reduced graphene oxide/Poly (vinyl alcohol) and multi-walled carbon nanotubes/Sodium Dodecyl Sulfate/Poly (vinyl alcohol) composites were prepared by water dispersion and different reduction treatments. Comparative studies were conducted to explore the electrical and optical properties of nanocomposites based on graphene and multi-walled carbon nanotubes. A thermal reduction of graphene oxide was more effective, producing films with sheet resistances as low as 10²–10³ Ω/square with 80% transmittance for 550 nm light. The percolation threshold of the thermally reduced graphene oxide composites (0.35 vol%) was much lower than that of the chemically reduced graphene oxide composites (0.57 vol%), and than that of the carbon nanotubes composites (0.47 vol%). The Seebeck coefficient of graphene oxide films changes from about 40 μV/K to −30 μV/K after an annealing of three hours at 200 °C. The optical absorption of the nanocomposites showed a high absorbance in near UV regions and the photoluminescence enhancement was achieved at 1 wt% graphene loading, while the carbon nanotubes based composite presents a significant emission at 0.7 wt% followed with a photoluminescence quenching at higher fraction of the nanofillers 1.6 wt% TRGO and 1 wt% MWCNTs.     

Comparison of cytotoxicity of pristine and covalently functionalized multi-walled carbon nanotubes in RAW 264.7 macrophages

Carbon nanotubes may be applied in different fields including biomedicine and mechanical engineering. It is important to understand the potential hazards of carbon nanotubes. In the present study, the toxicological effects of the pristine multi-walled carbon nanotubes (p-MWCNTs) and taurine functionalized multi-walled carbon nanotubes (tau-MWCNTs) were assessed on RAW 264.7 macrophages. We tested cell viability, GSH/GSSG ratio, apoptosis, intracellular calcium concentration, ultrastructural changes of cell morphology, and the release of IL-8. We observed the loss of cell viability, decline in the cellular GSH/GSSG ratio, increase of IL-8, and the increase of intracellular calcium concentration in RAW 264.7 macrophages when exposed to p-MWCNTs at high dosage. Additionally, exposure to p-MWCNTs resulted in ultrastructural and morphological changes in RAW 264.7 macrophages. In contrast, the RAW 264.7 macrophages exposed to the tau-MWCNTs did not exhibit altered morphology. Our results conclude that the tau-MWCNTs show lower toxicity than that of p-MWCNTs.