Molecular effect on surface topography of GaN bombarded with PF4 ions

We study surface topography and thickness of GaN layers implanted at room temperature with 1.3 keV/amu F, P, and PF₄ cluster ions. Results show that the density of collision cascades has a dramatic effect on the surface roughness and the thickness of implanted layers. Surface roughness increases with increasing cascade density. For very dense cascades produced by PF₄ ions, the evolution of layer thickness is dominated by ion-induced sputtering. In contrast, for the case of P ions producing less dense cascades, ion-induced swelling is observed.     

Synthesis and characterization of oil sorbent based on Hydroxypropyl Cellulose Acrylate

The present work deals with the preparation of some oil sorbers based on cellulose derivatives to control petroleum oil spills. In this respect, hydroxypropyl cellulose HPC was used to synthesize hydroxypropyl cellulose acrylate HPCA macromonomer by esterification of HPC with acryloyl chloride. Then the produced HPCA monomer was copolymerized with octadecyl acrylate (ODA) in the presence of two types of crosslinkers to produce oil gel. The chemical structures of both HPC and HPCA were confirmed by using FTIR and ¹HNMR spectroscopic analysis. Whereas the thermal properties of the crosslinked oil absorbents were investigated using TGA. Furthermore, morphological properties of prepared crosslinked copolymers were studied using SEM. Several parameters were considered to evaluate the oil sorbers, such as: monomers feed ratio, type and concentration of the applied crosslinkers. Finally, the swelling efficiency of oil gel was thoroughly investigated in light and heavy oil. It observed that as the octadecyl acrylate content increased the oil absorbency also increased and reached a maximum value at monomer feed ratio 10/90 HPCA/ODA. It is found that the maximum oil absorbency measured with MBA at a monomer feed ratio 10/90 HPCA/ODA are 29.7 and 18.6 g/g for toluene and crude oil, respectively.     

缓膨型膨润土橡胶遇水膨胀止水条(BW-S)应用技术

笔者对新型防水专利产品——缓膨型膨润土橡胶遇水膨胀止水条(BW-S)的物理参数、性能指标和技术特点进行了介绍,阐述了其在工程中地下室墙体施工缝和基础底板后浇带的应用过程.采用此材料进行防水处理,具有传统止水条无法比拟的技术优势.     

Numerical simulation of the swelling behaviour around tunnels based on special triaxial tests

This paper is to contribute to the understanding of the behaviour of tunnels in swelling ground. An Italian case study of a tunnel, collapsed due to swelling of a stiff clay, is taken as an example. The stress paths during excavation of elements of ground around the opening are computed in order to evidence the significant difference to that reproduced by usual swelling tests in the laboratory. An innovative triaxial testing procedure is developed and the stiff-clay tested. A numerical simulation of the swelling phenomenon induced by the excavation of the tunnel, based on the experimental results obtained, is then compared to site observations.     

Effect of chemical crosslinking on swelling parameters of modified poly(vinyl alcohol) hydrogel

Graft copolymerization of maleic anhydride (MA) onto partially and fully hydrolyzed poly(vinyl alcohol), PVA, was carried out in presence and in absence of an initiator. The structural features of these grafts were confirmed by 1 HNMR analysis. 1 HNMR analysis was also used to determine the percentage of grafting. These grafts were crosslinked using different concentrations of either 1,1,1-trimethylolpropane trimethacrylate (TPT) or methylene bisacrylamide (MBA) as Hexa- or tetra-functional crosslinker, respectively. The crosslinkers concentrations ranged from 1% to 30% (wt.%) based on the total weight of grafts. The final water content, volume fraction of the polymer and swelling capacity were determined for all grafts. The effect of MBA and TPT crosslinkers structure on swelling properties of both partially and fully hydrolyzed PVA grafts were also determined.     

Kinetik der freien,integralen Quellung von chemisch modifiziertem Holz entlang der Wasserdampf‐Sorptionsisotherme unter luftfreien Bedingungen

Die kinetischen, dreidimensionalen Messungen der freien, integralen Quellung wurden an unbehandeltem und an acetyliertem (Acetylgehalt 8,56 %, 20,14 % und 28,63 %) Tannenholz (Abies alba Mill.) entlang der Sorptionsisotherme unter luftfreien Bedingungen durchgeführt. Der zeitliche Verlauf der Quellung in den drei anatomischen Hauptrichtungen und in der transversalen Richtung wurde für das unbehandelte und das acetylierte Holz aufgezeigt sowie der maximale Dimensionsstabilisierungseffekt (ASE) für die jeweilige Modifizierung geschätzt. Die Auswirkung des Partialdruckgradienten des Wasserdampfes auf die mittlere Quellungsgeschwindigkeit wurde behandelt. Kinetic of free integral swelling on chemically modified wood along the water vapour sorption isotherm under air‐free conditions. The kinetic, three‐dimensional measurements of the free integral swelling were accomplished at the untreated and at the acetylated (acetyl content 8.56 %, 20.14 % and 28.63 %) fir wood (Abies alba Mill.) along the sorption isotherm under air‐free conditions. The course of the swelling in the three anatomical main directions and in the transversal direction was presented for the untreated and the acetylated wood. The anti‐swelling efficiency (ASE) for the accomplished modifications was estimated. The effect of the partial pressure gradient of the water vapour on the mean swelling speed was presented.     

High performance membrane-electrode assembly based on a surface-modified membrane

A surface-modified membrane is prepared using a sputtering technique that deposits gold directly on a Nafion^® 115 membrane surface that is roughened with silicon carbide paper. The surface-modified membranes are characterized by means of a scanning electron microscope (SEM), differential scanning calorimetry (DSC), and water contact-angle analysis. A single direct methanol fuel cell (DMFC) with a surface-modified membrane exhibits enhanced performance (160 mW cm⁻²), while a bare Nafion^® 115 cell yields 113 mW cm⁻² at 0.4 V and an operating temperature of 70 °C. From FE-SEM images and CO_ad stripping voltammograms, it is also found that the gold layer is composed of clusters of porous nodule-like particles, which indicates that an anode with nodule-like gold leads to the preferential oxidation of carbon monoxide. These results suggest that the topology of gold in the interfacial area and its electrocatalytic nature may be the critical factors that affect DMFC performance.     

A New Sorbent Chemically Cross-linked Highly Swollen Copolymeric Hydrogels for Dye Uptake

Water uptake and the sorption properties of polyelectrolyte hydrogels made by the polymerization of acrylamide (AAm) with maleic acid (MA) were investigated as a function of composition to find materials with swelling and dye sorption properties. Highly swollen acrylamide/maleic acid (AAm/MA) hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with MA as comonomer and two multifunctional cross-linkers such as trimethylolpropane triacrylate (TMPTA) and 1,4-butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. Chemically cross-linked AAm/MA hydrogels were used in experiments on sorption of water-soluble monovalent cationic dyes such as “Nil blue” (NB) and “Methyl violet (MV)”. Weight-swelling ratio values of AAm/MA hydrogels were calculated range 8.88–61.46. Some swelling kinetic parameters were found. Diffusion behavior of water and water sorption rate constant were investigated. Water diffusion into hydrogels was found to be non-Fickian in character. For sorption of cationic dyes, NB and MV into AAm/MA hydrogels were studied by batch sorption technique at 25°C. AAm/MA hydrogels in the dye solutions showed coloration. However, the AAm hydrogel did not show sorption of any dye from solution. The amount of the dye sorbed per unit mass of AAm/MA hydrogels was investigated.     

Equilibrium Swelling Characterization and Dye Uptake Studies of Acrylamide-co-Methylenesuccinic Acid Hydrogels and Semi-IPNs with PEG

A novel semi-interpenetrating network hydrogel, composed of acrylamide with methylenesuccinic acid as comonomer, with poly (ethylene glycol) and trimethylolpropane triacrylate was prepared. Highly swollen hydrogels were synthesized by free radical polymerization. Swelling experiments were performed in water and dye solutions at 25°C. The hydrogels were used in experiments on sorption of Basic Blue 12. Water and Basic Blue 12 diffusion into hydrogels was found to be non-Fickian in character. For sorption of BB 12 into the hydrogels was studied by batch sorption technique at 25°C. The adsorption capacity, removal effiency and partition coefficient of the hydrogels was investigated.     

Behaviors of Acrylamide/Itaconic Acid Hydrogels in Uptake of Uranyl Ions from Aqueous Solutions

Abstract

In this study, adsorptions of uranyl ions from two different aqueous uranyl solutions by acrylamide-itaconic acid hydrogels were investigated by a spectroscopic method. The hydrogels were prepared by irradiating with γ-radiation. In the experiment of uranyl ions adsorption, Type II adsorption was found. One gram of acrylamide-itaconic acid hydrogels sorbed 178–219 mg uranyl ions from the solutions of uranyl acetate, 42–76 mg uranyl ions from the aqueous solutions of uranyl nitrate, while acrylamide hydrogel did not sorb any uranyl ion. For the hydrogel containing 40 mg of itaconic acid and irradiated to 3.73 kGy, swelling of the hydrogels was observed in water (1660%), in the aqueous solution of uranyl acetate (730%), and in the aqueous solution of uranyl nitrate (580%). Diffusions of water onto hydrogels were a non-Fickian type of diffusion, whereas diffusions of uranyl ions were a Fickian type of diffusion.