Transition and stability of copolymer adsorption morphologies on the surface of carbon nanotubes and implications on their dispersion.

In this study, the adsorption morphologies as well as stability and transitions of a commercial dispersant copolymer (BYK 9076) on the surface of multiwalled carbon nanotubes (MWCNTs) were studied using Fourier transform infrared and UV-vis spectroscopy, dynamic light scattering, and electron microscopy techniques. The results show that the dispersion of carbon nanotubes in ethanol does not increase continuously with increasing copolymer/CNT ratio, which is correlated with the adsorption morphologies of the copolymer on the CNT surface. At a ratio of copolymer/CNT below 0.5, the morphology is random, shifting to a hemimicelle structure at a ratio from 0.5 to 1.0 while at ratios above 1.0, a cylindrical pattern is seen. The hemimicelle morphology is able to prevent the agglomeration of CNTs when the CNT concentration increases to 8.7 mg/mL, while cylindrical morphology is more efficient and stable to provide dispersion of CNTs at higher concentrations of CNTs.

Use of Municipal Solid Waste Incineration Fly Ash in Geopolymer Masonry Mortar Manufacturing.

The feasibility of partially replacing pulverized fly ash (PFA) with municipal solid waste incineration fly ash (MSWIFA) to produce ambient-cured geopolymers was investigated. The influence of mixture design parameters on the compressive strength of geopolymer paste was studied. The investigated parameters included MSWIFA dosage, the ratio of sodium silicate to sodium hydroxide (SS/SH), the ratio of liquid to solid (L/S) alkaline activator, and the ratio of SH molar. A water immersion method was selected as a pretreatment process for MSWIFA, leading to effectively maintaining the volume stability of the MSWIFA/PFA geopolymer. The mixture of 30% treated MSWIFA and 70% PFA with 12 M SS, 0.5 L/S ratio, and 3.0 SS/SH ratio produced the highest three-day compressive strength (4.9 MPa). Based on the optimal paste mixture, category four masonry mortars (according to JGJT98-2011) were prepared to replace various ratios of natural sand with fine recycling glasses. Up to a 30% replacement ratio, the properties of the mortars complied with the limits established by JGJT98-2011. The twenty-eight-day leaching rate of mortars containing 30% MSWIFA was lower than the limits proposed by GB5085.3-2007. Microstructural analysis indicated that the main reaction product was a combination of calcium silicate hydrate gel and aluminosilicate gel.

A comparative study on the mechanical, physical and morphological properties of cement-micro/nanoFe3O4 composite.

In this study, fabrication of a composite containing the ordinary Portland cement (OPC) and magnetite (Fe3O4) micro/nanoparticles is reported. In the first stage, the cement paste samples with a fixed 0.2 wt.% Fe3O4 additive in four different particle sizes (20-40 nm, 80-100 nm, 250-300 nm, and 1-2 µm) were prepared to check the effect of magnetite size. Magnetite was found to play an effective role in reinforcing cement matrix. The results showed that the cement paste reinforced by magnetite nanoparticles of 20-40 nm size range had the highest compressive, flexural, and tensile strengths compared to those of the other samples reinforced by larger particles. In the second stage, various amounts of the Fe3O4 nanoparticles of 20-40 nm size range were added to the cement to evaluate the influence of magnetite amount and find the optimized reinforcement amount. It was revealed that adding 0.25 wt.% Fe3O4 nanoparticles of 20-40 nm size range, as the optimal specimen, increased the compressive strength, flexural strength and tensile splitting strength by 23-32, 17-25, and 15-19%, respectively, and decreased the electrical resistance by 19-31%.

Lithium ion-selective membrane with 2D subnanometer channels.

In the last two years, the rapidly rising demand for lithium has exceeded supply, resulting in a sharp increase in the price of the metal. Conventional electric driven membrane processes can separate Li+ from divalent cations, but there is virtually no commercial membrane that can efficiently and selectively extract Li+ from a solution containing chemically similar ions such as Na+ and K+. Here, we show that the different movement behavior of Li+ ion within the sub-nanometre channel leads to Li+ ion-selectivity and high transport rate. Using inexpensive negatively charged 2D subnanometer hydrous phyllosilicate channels with interlayer space of 0.43 nm in a membrane-like morphology, we observed that for an interlayer spacing of below 1 nm, Li+ ions move along the length of the channel by jumping between its two walls. However, for above 1 nm spacing, the ions used only one channel wall to jump and travel. Molecular dynamic (MD) simulation also revealed that ions within the nanochannel exhibit acceleration-deceleration behavior. Experimental results showed that the nanochannels could selectively transport monovalent ions of Li+> Na+> and K+ while excluding other ions such as Cl- and Ca2+, with the selectivity ratios of 1.26, 1.59 and 1.36 for Li+/Na+, Li+/K+, and Na+/K+ respectively, which far exceed the mobility ratios in traditional porous ion exchange membranes. The findings of this work provide researchers with not only a new understanding of ions movement behavior within subnanometer confined areas but also make a platform for the future design of ion-selective membranes.