Foams Research Papers - Academia.edu (original) (raw)

In this work, alkali-activated fly ash-derived foams were produced at room temperature by direct foaming using aluminum powder. The 1 cm 3 foams (cubes) were then evaluated as adsorbents to extract heavy metals from aqueous solutions. The... more

In this work, alkali-activated fly ash-derived foams were produced at room temperature by direct foaming using aluminum powder. The 1 cm 3 foams (cubes) were then evaluated as adsorbents to extract heavy metals from aqueous solutions. The foams' selectivity towards lead, cadmium, zinc, and copper ions was evaluated in single, binary, and multicomponent ionic solutions. In the single ion assays, the foams showed much higher affinity towards lead, compared to the other heavy metals; at 10 ppm, the removal efficiency reached 91.9% for lead, 83.2% for cadmium, 74.6% for copper, and 64.6% for zinc. The greater selectivity for lead was also seen in the binary tests. The results showed that the presence of zinc is detrimental to cadmium and copper sorption, while for lead it mainly affects the sorption rate, but not the ultimate removal efficiency. In the multicomponent assays, the removal efficiency for all the heavy metals was lower than the values seen in the single ion tests. However, the superior affinity for lead was preserved. This study decreases the existing knowledge gap regarding the potential of alkali-activated materials to act as heavy metals adsorbents under different scenarios.

DOWNLOAD FREE FOR 1 MONTH AT: https://authors.elsevier.com/c/1aRxwI6yu4ckf Geopolymer foams (highly porous materials) have emerged as one of the most exciting materials over the past few years due to their remarkable properties,... more

DOWNLOAD FREE FOR 1 MONTH AT: https://authors.elsevier.com/c/1aRxwI6yu4ckf
Geopolymer foams (highly porous materials) have emerged as one of the most exciting materials over the past few years due to their remarkable properties, low cost and green synthesis protocol, enabling their use in various high added-value applications. Review papers on porous geopolymers are uncommon, and the emphasis has been given to materials processing and properties, while the applications were only briefly addressed. This review aims to fill this gap by presenting a comprehensive literature survey and critical analysis of the most recent and exciting research carried out on geopolymer foams. Up to now, these bulk-type (not powders) materials have been mainly considered as thermal and acoustic insulators. However, besides addressing their use as building material, this review also shows that their use in less investigated, but environmentally and economically relevant applications (e.g. bulk-type adsorbents, pH buffering agents and catalysts), is feasible and might ensure performance and technical advantages over their powdered counterparts. The limitations, challenges and future prospects associated with the different applications are presented. This review shows the remarkable potential of geopolymer foams in high added-value applications, far beyond their historical use as Portland cement replacement, which may encourage the widespread technological use of these materials.

Background & Aims: We evaluated the effect of a novel rehabilitative exercise on restoration of deglutition in a group of patients with deglutitive failure caused by abnormal upper esophageal sphincter (UES) opening manifested by... more

Background & Aims: We evaluated the effect of a novel rehabilitative exercise on restoration of deglutition in a group of patients with deglutitive failure caused by abnormal upper esophageal sphincter (UES) opening manifested by postswallow residue and aspiration necessitating percutaneous tube feeding. Methods: We studied a total of 27 patients by videofluoroscopy and functional assessment of swallowing scores before and after 6 weeks of a head-raising exercise program. Seven of 27 patients, assigned randomly, participated in a sham exercise before entering the tested exercise program. Eleven of 27 were randomized to the real exercise program. Results: Although there was no change in swallow function and biomechanics after the sham exercise, following 6 weeks of real exercise, all 11 patients exhibited a significant improvement in their UES opening, anterior laryngeal excursion (P < 0.01), as well as resolution of postdeglutitive aspiration and were able to resume oral feeding. Similar results were found when the 7 patients in the sham group were crossed over to the real exercise group. Comparison of before and after exercise values for anteroposterior UES opening (P < 0.01) and laryngeal anterior excursion (P < 0.05), as well as functional outcome assessment of swallowing (P < 0.05) in the entire group of 27 patients also showed significant improvement. Etiology and duration of dysphagia did not affect the outcome. Conclusions: The proposed suprahyoid muscle strengthening exercise program is effective in restoring oral feeding in some patients with deglutitive failure because of abnormal UES opening.GASTROENTEROLOGY 2002;122:1314-1321

Food rheology focuses on the flow properties of individual food components, which might already exhibit a complex rheological response function, the flow of a composite food matrix, and the influence of processing on the food structure... more

Food rheology focuses on the flow properties of individual food components, which might already exhibit a complex rheological response function, the flow of a composite food matrix, and the influence of processing on the food structure and its properties. For processed food the composition and the addition of ingredients to obtain a certain food quality and product performance requires profound

Wood-fiber-reinforced plastic profiles are growing rapidly in nonstructural wood-replacement applications. Most manufacturers are evaluating new alternative foamed composites, which are lighter and more like wood. Foamed wood composites... more

Wood-fiber-reinforced plastic profiles are growing rapidly in nonstructural wood-replacement applications. Most manufacturers are evaluating new alternative foamed composites, which are lighter and more like wood. Foamed wood composites accept screws and nails better than their nonfoamed counterparts, and they have other advantages as well. For example, internal pressures created by foaming give better surface definition and sharper contours and corners than nonfoamed profiles have. In this study, the microfoaming of polypropylene (PP) containing hardwood fiber was performed with an injection-molding process. The effects of different chemical foaming agents (endothermic, exothermic, and endothermic/exothermic), injection parameters (the mold temperature, front flow speed, and filling quantity), and different types of PP (different melt-flow indices) on the density, microvoid content, physicomechanical properties, surface roughness, and microcell classification of microfoamed PP/wood-fiber composites were studied. A maleic anhydride/polypropylene copolymer (MAH-PP) compatibilizer was used with the intention of improving the mechanical properties of microfoamed composites. The microcell classification (from light microscopy) and scanning electron micrographs showed that an exothermic chemical foaming agent produced the best performance with respect to the cell size, diameter, and distance. The polymer melt-flow index and the variation of the injection parameters affected the properties and microstructure of the microfoamed composites. The density of the microfoamed hardwood-fiber/PP (with a high melt-flow index) composites was reduced by approximately 30% and decreased to 0.718 g/cm3 with an exothermic chemical foaming agent. Tensile and flexural tests were performed on the foamed composites to determine the dependence of the mechanical properties on the density and microvoid content of the foamed specimens, and these properties were compared with those of nonfoamed composites. MAH-PP improved the physicomechanical properties up to 80%. With an increase in the mold temperature (80–110°C), the surface roughness was reduced by nearly 70% for the foamed composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1090–1096, 2005

The adhesion and interfacial properties of polyurethane (PU) foams with thermoplastic (TP) materials were investigated using different techniques. The adhesion performance of PU foam with TP materials was evaluated using the peel test... more

The adhesion and interfacial properties of polyurethane (PU) foams with thermoplastic (TP) materials were investigated using different techniques. The adhesion performance of PU foam with TP materials was evaluated using the peel test method, and the adhesion durability was checked after different climate treatments. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements were used to study the surface and interface morphology of PU foam and TP material system. Three types of PU foam samples which differ in their composition and also five commercially available TP blends systems, based on poly(carbonate), poly(styrene-co-maleic anhydride), poly(acrylonitrile-butadiene-styrene), and silicone acrylate rubber have been used. The slow reacting foam shows the best adhesion properties with all the TP materials. The climate treatments strongly effected the PU foam adhesion durability with poly(carbonate) containing TP materials (70–80% loss in adhesion), but nearly no effect with poly(styrene-co-maleic anhydride). The samples with lowered adhesion could be separated by peeling without visible foam residues on the TP surface. AFM, XPS, and surface tension studies have shown that the surface properties of the TP material are still governed by the PU foam. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 479–488, 2007

In this work, a numerical study is proposed to investigate and predict the thermal performance of graphite foams infiltrated with phase change materials, PCMs, for space and terrestrial energy storage systems. The numerical model is based... more

In this work, a numerical study is proposed to investigate and predict the thermal performance of graphite foams infiltrated with phase change materials, PCMs, for space and terrestrial energy storage systems. The numerical model is based on a volume averaging technique while a finite volume method has been used to discretize the heat diffusion equation. A line-by-line solver based on tri-diagonal matrix algorithm has been used to iteratively solve the algebraic discretization equations. Because of the high thermal conductivity of graphite foams, the PCM-foam system thermal performance has been improved significantly. For space applications, the average value of the output power of the new energy storage system has been increased by more than eight times. While for terrestrial applications, the average output power using carbon foam of porosity 97% is about five times greater than that for using pure PCM.

A programme of research is outlined which considers the foaming performance and foam behaviour of surfactant systems commonly encountered in hand-wash laundry detergent applications. An experimental study of the physical chemistry of foam... more

A programme of research is outlined which considers the foaming performance and foam behaviour of surfactant systems commonly encountered in hand-wash laundry detergent applications. An experimental study of the physical chemistry of foam generation indicates that precipitation of a typical anionic surfactant with calcium forms mesophase particles and causes a marked reduction in the rate of transport of surfactant to air–water surfaces and a concomitant reduction in foaming. Oily soil antifoam effects are however insensitive to the presence of calcium, being equally effective regardless of pH and calcium content. They may be reproduced by a simple particle–oil mixture of a saturated and an unsaturated triglyceride (e.g. tristearin and triolein respectively). A detailed foam rheometry study is performed using foam flowing through a constriction. Bubble shapes are used to deduce the normal and shear stresses across the foam flow field. Broad agreement between the experimental stress field and that obtained from quasistatic simulations is demonstrated. As foam flow-rate increases, a different model, which takes explicit account of viscous dissipative forces within the foam flow field is required. The dissipative foam flow model predicts differential shrinkage and stretch rates of foam films. Coupled to a model for surfactant transport, this shows the extent to which surfactant concentration accumulates in shrinking films and is depleted in stretching films. In addition to film stretching, it is also important to know about film bursting or failure rates. Here failure rates are estimated using capillary suction pressures exerted on the films by Plateau border channels around film edges. The failure rates can then be employed to predict the evolution of bubble size at various spatial locations in a foam: reasonable agreement with experimental bubble size distributions is obtained.

One key strategy for increasing the application potential for biodegradable plastics lies in improving the physical and mechanical characteristics, which can be attained by inducing a cellular morphology in the pure polymer with the aid... more

One key strategy for increasing the application potential for biodegradable plastics lies in improving the physical and mechanical characteristics, which can be attained by inducing a cellular morphology in the pure polymer with the aid of a blowing agent, as well as by blending two or more polymers with the desirable properties. This paper examines the effect that blending two biodegradable polymers has on the thermal properties and morphology of the resultant foams blown with carbon dioxide (CO 2). Polylactic acid (PLA) ...

Multi-walled carbon nanotube (MWCNT)/C/polystyrene (PS) composite materials were prepared by in situ polymerization of monomer in preformed MWCNT/C foams. MWCNT/C foams were preformed using polyurethane foam as template. The preformed... more

Multi-walled carbon nanotube (MWCNT)/C/polystyrene (PS) composite materials were prepared by in situ polymerization of monomer in preformed MWCNT/C foams. MWCNT/C foams were preformed using polyurethane foam as template. The preformed MWCNT/C foams had a more continuous conductive structure than the carbon nanotube networks formed by free assembly in composites. The structure of the MWCNT/C foam network was characterized with scanning electron microscopy. The MWCNT/C/PS composites have an electric conductivity higher than 0.01S/cm for a filler loading of 1wt.%. Enhancement of thermal conductivity and mechanical properties by the preformed MWCNT/C foam were also observed.

This paper examines the behaviour of growing and collapsing foams. In particular, it focuses on the drainage of the liquid, and thus the evolution of the liquid content, within the growing or collapsing foam. By assuming that the films... more

This paper examines the behaviour of growing and collapsing foams. In particular, it focuses on the drainage of the liquid, and thus the evolution of the liquid content, within the growing or collapsing foam. By assuming that the films fail when they are subjected to a pressure above a certain critical pressure, the collapse of the foam is modelled. The model predicts that the growing foam behaviour can be divided into two regimes: at low gas rates, the foams will asymptote towards an equilibrium height, while above a certain critical gas rate, the foams will continue to grow indefinitely. This behaviour was found experimentally as well.At the higher gas rates, there is a change in the slope of the foam height versus time plot, though with the exception of a transition region, this relationship remains a linear relationship one. The difference between these slopes can be used to estimate the pressure exerted on the films at the top surface of the foam. Since these bubbles are bursting, this is the critical pressure required to cause film failure within the foam. When compared to the stability of films in single film experiments, those in the foam, not unexpectedly, demonstrate lower stability. This is due to vibrations and other disturbances that are present within flowing foams.

Considering the size of the amount of energy consumption in ovens during the production of gas ceramic foam materials in the ceramic industry, it can be stated that natural gas is one of the highest energy resources. Natural gas... more

Considering the size of the amount of energy consumption in ovens during the production of gas ceramic foam materials in the ceramic industry, it can be stated that natural gas is one of the highest energy resources. Natural gas consumption during the production has been evaluated and financial analyses were made for saving consumption amounts. Raw materials and glass/frit wastes obtained from different regions were investigated and their chemical compositions were determined by X-Rays fluorescence spectrometry (XRF) analysis. Compared to their current alternatives, glass foams with homogenous structure and low density were developed by adding frit/ glass wastes in the amount of 80%-90%. X-Ray diffraction (XRD) analysis has been conducted for mineralogical investigation of the samples. Also, to analyze the pore sizes and examine the surface morphology of foams, SEM images were obtained. With the addition of glass/frit wastes, natural gas consumption decreased (ca. 20%-25%) in firing process.