AQUACULTURE RESEARCH, Issue 11 2008
Patrizia De Gaetano
Abstract The modelling framework already introduced by Doglioli, Magaldi, Vezzulli and Tucci to predict the potential impact of a marine fish farm is improved following different directions, namely (1) real historic current-metre data are used to force the simulations, (2) settling velocity values specifically targeting Mediterranean fish species are used, and (3) a new benthic degradative module, the Finite Organic Accumulation Module, is added to the modelling framework. The Finite Organic Accumulation Module uses the output of the other functional units of the modelling framework to calculate the organic load on the seabed. The Finite Organic Accumulation Module considers the natural capability of the seafloor in absorbing part of the organic load. Different remineralization rates reflect the sediment stress level according to the work of Findlay and Watling. Organic degradation for both uneaten feed and faeces is evaluated by changing the release modality (continuous and periodical) and by varying the settling velocities. It is found that the maximum impact on the benthic community is observed either for quickly sinking uneaten feed released twice a day, or for less intense near-bottom current conditions. If both the above-mentioned scenarios coexist, a high stress level is established in the sediment. The model also suggests that the use of self-feeders in cages can reduce farm impacts significantly. These results show how the new and more complete modelling framework presented here is able to improve the objectivity in the decision-making processes and how it may be successfully used for planning and monitoring purposes. [source]

RHEOLOGICAL CHARACTERIZATION OF WET FOOD FOAMS

JOURNAL OF TEXTURE STUDIES, Issue 2 2007
B. EDGAR CHÁVEZ-MONTES
ABSTRACT Incorporating air bubbles into foods is a technical challenge, and in all cases, the fabrication of a foam goes through a "wet foam" stage, where bubbles are diluted in the food matrix and require stabilization. Sometimes, the end product is itself a wet foam, and a popular example is ice cream. This article describes a study of structural aspects of wet foams, where the continuous phase is a fluid, by means of dynamic rheological tests. The effects of formulation and processing conditions on aerated food foams are studied, and an example is presented for ice cream mix. The incorporation of gas bubbles at volume fractions of 50% or less modifies moderately the bulk rheological properties, and their effect can be predicted by the foam limit case. The continuous phase dominates to a great part the bulk's rheological behavior, and in the case of food systems, it stems from the presence of polysaccharide thickeners. PRACTICAL APPLICATIONS This work presents an alternative approach to study the rheological properties of short life and difficult-to-sample products, such as wet food foams, in a rheo-reactor. Through the analysis of mechanical properties in oscillatory regime, the structure and stability of wet food foams can be characterized immediately after being fabricated in situ. This work presents new insights on the foaming step of ice cream mix (decoupled from the freezing step), and shows how the mechanical properties are affected by the incorporation ofbubbles, by process conditions and by the presence of thickeners and emulsifiers. This work can be a valuable guide to decide on optimal process and formulation to fabricate wet food foams (e.g., ice cream, aerated desserts) with specific mechanical properties and stability. [source]

OSCILLATING VANE GEOMETRY FOR SOFT SOLID GELS AND FOAMS

JOURNAL OF TEXTURE STUDIES, Issue 6 2002
C. SERVAIS
ABSTRACT Several relationships between the torque and the stress exist for the vane geometry, but only a few equations have been proposed for the relationship between angular displacement and strain. In this study, an expression based on the infinite gap approximation for concentric cylinders is used and well-defined reference data are compared to oscillating vane data to validate the assumptions used. Gelatin gels are used for their property to stick to the wall and carrageenan gels are used to show that wall slip does not occur with oscillating vanes in serrated cup geometries. Shaving foams are used as a model low density, time and shear stable foam, which resists irreversible damage when loaded between serrated parallel plates. Results show that the assumptions used for the determination of stress and strain with the vane provide material viscoelastic properties that are not significantly different from reference values as obtained with concentric cylinders and parallel plates. [source]

Sclerosing Foam in the Treatment of Varicose Veins and Telangiectases: History and Analysis of Safety and Complications

DERMATOLOGIC SURGERY, Issue 1 2002
Alessandro Frullini MD
objective. To review the use of sclerosing foam in the treatment of varicose veins, to describe the different techniques of foam preparation, and to report the complications of our 3-year experience with this treatment. method. From November 1997 to the end of October 2000, 453 patients were treated with a sclerosing foam for large, medium, and minor varicosities with sodium tetradecylsulfate (STS) or polidocanol (POL). A first group of 257 patients (90 for minor varicosities and 167 for medium to large veins) received a sclerosing foam according to the Monfreux technique. From December 1999 to October 2000, 196 patients were treated with a sclerosing foam prepared according to Tessari's method (36 for minor size veins or teleangectasias and 170 for medium-large veins). Every patient was studied with (color-flow) duplex scanning before and after the treatment and large vein injections were administered under duplex guide. results. The immediate success rate was 88.1% in the first group for the medium-large veins. In the same districts we registered an early success rate in 93.3% for the patients treated with the Tessari's method. The complication rate (mostly minor complications) was 8.5% in the first group and 7.1% in the second group. conclusion. The use of sclerosing foam may become an established therapy in the treatment of varicose veins with a high success rate, low cost, and low major complication rate. According to our actual experience and knowledge, the safe amount of foam should not exceed the 3-ml limit, but further advancements could come from standardization of the foam preparation technique. [source]

The Prospects of Carrying and Releasing Drugs Via Biodegradable Magnesium Foam,

ADVANCED ENGINEERING MATERIALS, Issue 8 2010
Eli Aghion
Abstract Powder metallurgy technology was used to produce magnesium foams in order to evaluate their ability to perform as a solid biodegradable platform for drug delivery. The amount and delivery time of the released drug (gentamicin) was controlled by the level of space-holding particles (spacer) that was mixed with the magnesium powder prior to the sintering process. Metallurgical examination of the magnesium foams was carried out using optical and scanning electron microscopy (SEM) and X-ray diffraction analysis. Microtomography CT analysis was used to evaluate the structural characteristics of the magnesium foams and their internal interconnected porosity configuration. The corrosion behavior of the magnesium foams was evaluated by immersion test in a simulated physiological environment (PBS solution). The absorption of gentamicin was obtained by immersing magnesium foams in concentrated gentamicin solutions within a vacuum chamber, followed by water evaporation. The detection of gentamicin in PBS solution was carried out using a Fluorescence Polarimetry analyzer. The results show that the release profile of gentamicin from magnesium foam with 10 and 25% spacer in PBS solution was in accord with common dissolution kinetics of an active ingredient from polymeric drug delivery systems. [source]

Carbon Nanotube Coatings on Bioglass-Based Tissue Engineering Scaffolds

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007
R. Boccaccini
Abstract The coating of highly porous Bioglass® based 3D scaffolds with multi-walled carbon nanotubes (CNT) was investigated. Foam like Bioglass® scaffolds were fabricated by the replica technique and electrophoretic deposition was used to deposit homogeneous layers of CNT throughout the scaffold pore structure. The optimal experimental conditions were determined to be: applied voltage 15,V and deposition time 20 minutes, utilizing a concentrated aqueous suspension of CNT with addition of a surfactant and iodine. The scaffold pore structure remained invariant after the CNT coating, as assessed by SEM. The incorporation of CNTs induced a nanostructured internal surface of the pores which is thought to be beneficial for osteoblast cell attachment and proliferation. Bioactivity of the scaffolds was assessed by immersion studies in simulated body fluid (SBF) for periods of up to 2 weeks and the subsequent determination of hydroxyapatite (HA) formation. The presence of CNTs can enhance the bioactive behaviour of the scaffolds since CNTs can serve as template for the ordered formation of a nanostructured HA layers, which does not occur on uncoated Bioglass® surfaces. [source]

Microbiological Benefits of Removing Foam Formed After UV-Enhanced Ozonation of Poultry-Processing Chiller Water for Recycling

JOURNAL OF FOOD SCIENCE, Issue 3 2002
M.E. Diaz
ABSTRACT: Prior experiments using 250 mL samples of unscreened poultry overflow chiller water evaluated the beneficial bactericidal and oxidative effects of 4 different treatments (namely, O2/O3,O2/UV, O2/O3/UV, and O2 as the control) for improving microbiological safety, turbidity, and water-use efficiency allowing its reconditioning for reuse. When excluding foam as in this present study, synergistic reductions > 1.5 log CFU/mL for aerobic plate counts (APC) were additionally achieved after 4 min for all O3/UV treatment combinations as compared to serially applied treatments of O3 and UV acting separately. With foam present, 16-min O3/UV treatments were required to achieve similar results. We now report these additional benefits achieved by removing the foam formed by the advanced oxidation process of ultraviolet-photon enhanced ozonation. Furthermore, foam microbial and general physical content were analyzed to determine suitability as an additive in rendering-type processes. Treatment of the wastewater resulted in total plate counts between 2 to 4 Log CFU/mL in the foam after 8 min. Fat and protein constituted 89% of the solids collected (384 mg/L or 14% of the foam) with trace amounts of metal elements (for example, Ca, Na, K, Fe, Cu) present. Irradiating had negligible effect on foam characteristics yet decreased the amount of solids collected. [source]

A new mesalazine foam enema (Claversal Foam) compared with a standard liquid enema in patients with active distal ulcerative colitis

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 3 2002
H. Malchow
Background: Rectally administered mesalazine (5-aminosalicylic acid) is a recognized therapy for distal ulcerative colitis. It is frequently applied as a liquid enema. However, there are reasons (acceptability to the patient, more uniform topical dispersion and effective adhesion) to prefer a foam-based enema. Aim: This study compared a foam enema (2 g mesalazine per day, Claversal Foam) with a standard liquid enema (4 g mesalazine per day, Salofalk enema). Methods: Patients with active distal ulcerative colitis, diagnosed according to standardized criteria, were treated for 4 weeks. The primary goal was clinical remission; endoscopic remission, histological changes, global assessment and standard safety measures were also analysed. A major subset of the patients also provided quality-of-life data. Results: Both foam and liquid enema gave good rates of clinical and endoscopic remission. The foam enema was shown to be as efficacious as the reference, even though the daily dose in the foam treatment contained only half as much active drug as in the reference treatment. Minor regional differences in efficacy were seen. The tolerabilities of the two formulations were comparable. Conclusions: The foam enema offers a safe, efficacious and acceptable treatment for distal ulcerative colitis. [source]

A simple automated method of quantitative characterization of foam behaviour,

POLYMER INTERNATIONAL, Issue 4 2003
Dr Klaus Lunkenheimer
Abstract There are various methods available to measure foam stability. However, their main drawback is that their results are hardly comparable because definite boundary conditions are missing. One particular disadvantage is that there is no method which is applicable to systems of very low (transient or ,wet' foams) as well as of very high (metastable or ,dry' foams) foam stability. Here, we put forward a novel automatic, pneumatic method that is applicable to both systems. Its principle relies on the measurement of the foam produced by dispersing a definite amount of gas in a definite volume of solution at constant gas velocity. Foam and draining solution are determined simultaneously. This method has advantages over all other methods in several respects such as: (1) it represents a simple and definite procedure under well-defined boundary conditions, (2) it is generally applicable to all kinds of foam, and (3) it provides new standard parameters for the quantitative characterization of foamability and foam stability. The standard parameters can be related to the basic adsorption properties and the structure of the surfactant. The method's capability is demonstrated with three different non-ionic and ionic surfactants belonging to the wet (n-octanoic acid) and dry foam systems (n-nonyl-,- D -glucopyranoside and sodium dodecylsulfate). Copyright © 2003 Society of Chemical Industry [source]

HyBAR: hybrid bone-attached robot for joint arthroplasty

THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 2 2009
S. Song
Abstract Background A number of small bone-attached surgical robots have been introduced to overcome some disadvantages of large stand-alone surgical robots. In orthopaedics, increasing demand on minimally invasive joint replacement surgery has also been encouraging small surgical robot developments. Among various technical aspects of such an approach, optimal miniaturization that maintains structural strength for high speed bone removal was investigated. Methods By observing advantages and disadvantages from serial and parallel robot structures, a new hybrid kinematic configuration was designed for a bone-attached robot to perform precision bone removal for cutting the femoral implant cavity during patellofemoral joint arthroplasty surgery. A series of experimental tests were conducted in order to evaluate the performance of the new robot, especially with respect to accuracy of bone preparation. Results A miniaturized and rigidly-structured robot prototype was developed for minimally invasive bone-attached robotic surgery. A new minimally invasive modular clamping system was also introduced to enhance the robotic procedure. Foam and pig bone experimental results demonstrated a successful implementation of the new robot that eliminated a number of major design problems of a previous prototype. Conclusions For small bone-attached surgical robots that utilize high speed orthopaedic tools, structural rigidity and clamping mechanism are major design issues. The new kinematic configuration using hinged prismatic joints enabled an effective miniaturization with good structural rigidity. Although minor problems still exist at the prototype stage, the new development would be a significant step towards the practical use of such a robot. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Mechanisms of ultrasound foam interactions

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009
J. B. Winterburn
Abstract An experimental investigation into the effects of two frequencies of low-power ultrasound on detergent (Teepol) stabilised air-water foams is presented. Foam was subjected to ultrasound at 28 and 40 kHz with a power-to-foam volume ratio of approximately 3 W l,1 with particular consideration being given to the acoustic impedance discontinuity between air and water. The foam height, liquid drainage and collapse behaviour were compared to experiments conducted without ultrasound. In the case of 40 kHz ultrasound, an increased liquid drainage rate was observed and a pronounced increase and subsequent peak in mean liquid hold-up, which occurred at 4 min, was observed. These results appear to be independent of the initial liquid hold-up of the foam. Liquid drainage and mean liquid hold-up results were related to foam collapse mechanisms of homogeneous rupture (HR) and rupture front breakage (FR), concluding that rupture front breakage dominates the collapse of foam under the influence of 40 kHz ultrasound. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Efficient Synthesis of Dimethyl Ether over HZSM-5 Supported on Medium-Surface-Area ,-SiC Foam

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 10 2008
Svetlana Ivanova Dr.
Abstract In this study, we aimed to produce a highly selective and stable catalyst for the production of dimethyl ether by methanol dehydration. The activities were compared of different active phases of the employed system, zeolite HZSM-5 or , -alumina, supported on silicon carbide as foam, and it was found that the supported zeolite catalysts are more active than and as selective as the alumina-based catalysts. The as-prepared zeolite/SiC composites reveal good stability in long-term tests in the presence or absence of steam. The high stability is attributed to the presence of highly dispersed micrometer-sized zeolite particles, which make the active sites more accessible to the reactants and promote the quick transfer of the desired product, dimethyl ether, out of the catalyst bed, minimizing deactivation of the catalyst. [source]

The History of Sclerosing Foams

DERMATOLOGIC SURGERY, Issue 5 2004
Jan-Christoph G. R. Wollmann MD
Background. The use of foamed sclerosants in phlebology is undergoing a renaissance. The use of foam sclerotherapy was relaunched only a few years ago. Despite this, the early developments, pioneer findings, and improvements, especially in foaming techniques, are not widely recognized. Objective. The objective of this study was to give an overview from the very beginnings of foam sclerotherapy until the most recent and progressive techniques, as described by Tessari or the double syringe system technique. Results. The publications found after a thorough research for literature about foam sclerotherapy allow us to examine what has been invented between Orbach's work in 1944 and now and,surprisingly,even before 1944. The contributions of greatly reputed and also of unknown colleagues, such as Orbach, Sigg, Mayer, or Flückiger, are presented, giving a historical overview from the very beginnings of foam sclerotherapy until the most recent techniques. Basically, the literature shows that remarkable work was carried out in the field of noncommercial foam sclerotherapy and that sclerosing foams have been used by numerous doctors continuously for the past six decades, especially for the treatment of varicose veins of the lower limbs. Conclusion. The use of foamed sclerosing agents in therapy of large or small varicose veins is not new. It started as early as 1939 and has continuously been improved in the past decades. [source]

Mechanical Characterization of Particulate Aluminum Foams,Strain-Rate, Density and Matrix Alloy versus Adhesive Effects

ADVANCED ENGINEERING MATERIALS, Issue 7 2010
Dirk Lehmhus
Abstract The study evaluates mechanical properties of APM particulate aluminum foams built up from adhesively bonded Al foam spheres. Foams of matrix alloy AlSi10 are compared, with PM AlSi7 foams used as reference. The influence of density is studied both for quasi-static and dynamic compressive loading in a range from ,0.35 to 0.71,g,cm,3. The effect of varying the bonding agent is evaluated for a single density and both strain rate levels by replacing the standard, high-strength epoxy-based adhesive with a polyamide of greatly increased ductility. The result is a clear shift of fracture events to higher strain levels, as well as the introduction of a strain-rate dependency of strength. [source]

Syntactic Iron Foams with Integrated Microglass Bubbles Produced by Means of Metal Powder Injection Moulding,

ADVANCED ENGINEERING MATERIALS, Issue 7 2010
Jörg Weise
Systematic tests for the production of pure iron (99%) foams with integrated microglass bubbles by means of metal powder injection moulding (MIM) have been carried out with variation of the glass bubble contents. Process parameters were optimized and the resulting materials characterized using density measurements, tensile and compression tests, metallographic sections, and scanning electron microscopy. The corrosion behavior of this novel material was characterized using potentiodynamic polarization measurements and immersion tests. [source]

Al and Zn Foams Blown by an Intrinsic Gas Source

ADVANCED ENGINEERING MATERIALS, Issue 6 2010
M. Mukherjee
A method was developed to produce Al- and Zn-based foams with a uniform distribution of small cells. Pre-alloyed AlMg50 powder containing hydrogen was used as a replacement for the usual blowing agent TiH2. AlMg50 powder released gas uniformly in the entire sample, caused the nucleation of a large number of cells and led to simultaneous growth that finally resulted in a uniform cell structure. The expansion behavior of these foams was studied by means of in situ X-ray radioscopy. The macrostructure of the solidified foams was then analyzed through optical microscopy and X-ray tomography and proved to be very uniform. The high strength of the foams was demonstrated by uni-axial compression tests. [source]

Study on Crack-like Pores of Al Foams Made via the Powder-Metallurgy Route,

ADVANCED ENGINEERING MATERIALS, Issue 1-2 2010
Lei Wang
Mechanisms for the formation and disappearance of the crack-like pores generated during the early stage of Al foaming are investigated. A model for their disappearance process is proposed for the first time. The stress, perpendicular to the compaction direction in uniaxial cold compaction, is caused by the interaction of the Al powder under a high compaction pressure and is the main reason for the formation of the crack-like pores. The results of the model analysis and theoretical calculations suggest that the pressure difference ,P between the initial, round bubbles and the crack-like pores is the driving force for their disappearance. The rapid reduction of ,P is attributed to the decomposition characteristics of the TiH2 powder. [source]

Heat Transfer in Polypropylene-Based Foams Produced Using Different Foaming Processes,

ADVANCED ENGINEERING MATERIALS, Issue 10 2009
Marcelo Antunes
This paper presents the characterization of the cellular structure and thermal conduction behaviour of polypropylene foams produced using different foaming processes, with the aim of selecting the best possible PP foam thermal insulator. Thermal conductivity results have shown that the global heat transfer behaviour is controlled by the relative density. For relative densities higher than 0.2, thermal conductivity differences were insignificant, the data being predicted by the mixture's rule and Russell's model. In the low density range, all of the proposed models underestimated the overall conductivity, the effect of the processing method being more significant, slight differences being observed between foams produced by extrusion and those produced by gas dissolution with higher cell sizes and anisotropies. Foams with finer cellular structures showed to be better insulating materials. [source]

Heat Transport in Closed Cell Aluminum Foams: Application Notes,

ADVANCED ENGINEERING MATERIALS, Issue 10 2009
Jaime Lázaro
Heat transport equations have been used to solve, by implementing the Finite Element Method (FEM), three different cases representative of the aluminium foams life: the production process (solidification in the molten state), post-production (water quenching heat treatments) and applications (fire barriers). [source]

Preparation of Titanium Foams by Slip Casting of Particle Stabilized Emulsions,

ADVANCED ENGINEERING MATERIALS, Issue 8 2009
Bram Neirinck
Bulk titanium foams were prepared by emulsion templating during slip casting. The emulsion template was stabilized using partially hydrophobized titanium particles while the continuous phase consisted of a titanium hydride powder suspension. Sintering was performed in inert atmosphere. The use of titanium hydride resulted in lower sintering temperatures and denser, stronger struts. Both homogeneous foams with high compressive strength and structures with a gradient in pore size were obtained. [source]

A Novel Process for the Manufacture of Auxetic Foams and for Their re-Conversion to Conventional Form,

ADVANCED ENGINEERING MATERIALS, Issue 7 2009
Joseph N. Grima
Images showing the microstructure of conventional and auxetic foams produced through the traditional thermo,mechanical process and the novel chemo,mechanical process. Auxetic foams exhibit the unusual property of becoming fatter which when stretched a property which makes them superior to conventional foams in various applications ranging from smart tunable filters to vibration-proofing materials. [source]

Topological Analysis of Foams and Tetrahedral Structures,

ADVANCED ENGINEERING MATERIALS, Issue 3 2009
Gad Frenkel
A unified method is introduced to characterize the topology and connectivity of foams and general tetrahedral structures. A workflow for an automated characterization of the void space topology is presented, using a partition of the system volume into polyhedral cells connected by skeletal throats. The advantages of this characterization are discussed and it serves as the basic input for an entropic analysis of the statistics of structural configurational disorder. [source]

Creating Aligned, Elongated Pores in Titanium Foams by Swaging of Preforms with Ductile Space-Holder,

ADVANCED ENGINEERING MATERIALS, Issue 1-2 2009
Yasumasa Chino
Preforms of titanium powders containing a naphthalene-based space-holder phase are swaged. The elongated space-holder particles are sublimated and the preform is sintered, resulting in titanium foams with 49,65% porosity consisting of: a) small equiaxed pores from incomplete powder sintering and b) larger, elongated pores replicating the space-holder, which are aligned along the swaging direction. The foam carbon content (0.39,wt%) is below the value for severe titanium embrittlement. [source]

Analytical Modelling of the Radiative Properties of Metallic Foams: Contribution of X-Ray Tomography

ADVANCED ENGINEERING MATERIALS, Issue 4 2008
M. Loretz
Two metallic foams exhibiting a similar porosity but different cell sizes have been characterized using X-ray tomography. The images have been processed and analysed to retrieve the morphological properties required for the calculation of the radiative properties such as the extinction coefficient. The multiple possibilities of using the X-ray tomography method rather than conventional optical methods like SEM have been quantified. The extinction coefficient has then been determined from two approaches. First, the resulting morphological properties have been used as the input data of the conventional independent scattering theory. A special emphasis is put on the determination of morphological properties and their influence on the results. In the second approach, an original method is also proposed in order to determine the extinction coefficient of highly porous open cell metal foams, from the tomographic images and without any calculation or hypothesis. Results show a good agreement with the extinction coefficient obtained from experimental measurements. Our novel method enables to reduce uncertainties considerably. [source]

Mechanical Behaviour of Internal Reinforced Aluminium Foams,

ADVANCED ENGINEERING MATERIALS, Issue 11 2007
E. Solórzano
The paper presents a new way to improve the mechanical behaviour of aluminum based foams produced by the powder metallurgical (PM) route; the method is based on the use of internal reinforcements. These reinforcements allow an excellent improvement of the mechanical response in compression, tension and bending all at the same time. The produced samples have showed an excellent reproducibly in their mechanical response. [source]

Joining Strategies for Open Porous Metallic Foams on Iron and Nickel Base Materials,

ADVANCED ENGINEERING MATERIALS, Issue 8 2007
S. Longerich
Within the Collaborative Research Centre (SFB) 561 "Thermally highly loaded, porous and cooled multilayer systems for combined cycle power plants" open porous Ni-based structures are developed for the requirements of an effusion cooling. A two-dimensional cooling strategy for the walls of combustion chambers, that allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realized by an open porous metallic foam structure. The challenge is to join the porous foam structure with the solid substrate material. Capacitor discharge welding and laser beam welding/-brazing methods seems to be promising methods due to a minimum input of energy and, connected with this, a small joining zone. [source]

The Effect of Compaction Method on the Expansion and Stability of Aluminium Foams,

ADVANCED ENGINEERING MATERIALS, Issue 9 2006
S. Asavavisithchai
Abstract The foam expansion and collapse behaviour for heat treated Al-TiH2 precursors has been shown to be driven by the oxidation of the Al powder, which can, in moderation, improve the foam expansion and increase foam stability, and the premature loss of gas from the TiH2, which delays but decreases the foam expansion. The evidence presented indicates that as long as theoretical precursor densities >,99,% can be achieved, simultaneous heating and compaction are not required to achieve the best foaming behaviour. Instead, the oxygen or oxide content in the powder is critical and if the oxygen content in the atomised powder is in the range 0.3,0.4,wt.%, cold compaction is sufficient to produce foams which show expansions at least as good as those for precursors made by high cost hot working processes. [source]

Machine Tools With Metal Foams,

ADVANCED ENGINEERING MATERIALS, Issue 9 2006
R. Neugebauer
Abstract Machine tool construction calls for subassemblies with reduced weight while retaining excellent dynamic properties. Modern frame components do always meet required static stiffness but often display oscillation problems due to low component wall thicknesses. Breaking down solid steel structure into wide-area sandwich designs such as steel-aluminum foam-steel panels results in good static properties to be combined with excellent properties since these sandwiches have 30 to 40 times the flexural strength. This is due to their major geometrical moment of inertia in relation to adequate-mass steel sheet metals. In addition, the foam core dampens oscillations. Studies on foamed steel sections indicate that 2 to 3 times higher damping is likely in relation to unfoamed steel sections. These benefits were the motivation for the Chemnitz Metal Foam Center to accelerate development of extremely large-format sandwiches with dimensions of 1,500,×,1,000,mm2. [source]

The Role of Oxidation During Compaction on the Expansion and Stability of Al Foams Made Via a PM Route,

ADVANCED ENGINEERING MATERIALS, Issue 6 2006
S. Asavavisithchai
The foam expansion and collapse behaviour for hot compacted Al-TiH2 precursors has been shown to be driven by the oxidation of the Al powder and the premature loss of gas from the TiH2 foaming agent during the compaction process. At 550,°C, oxidation is rapid, and gas loss from the hydride is extensive leading to poor expansion. [source]

Tensile Behaviour of Replicated Aluminium Foams,

ADVANCED ENGINEERING MATERIALS, Issue 6 2004
J.-F. Despois
Abstract The replication process is used to produce open-cell 99.99,% pure aluminium foams of controlled pore diameter and solid volume fraction; each parameter is varied respectively from 40 to 400,,m and 10 to 30,vol. pct. The foam tensile behaviour is consistent with the small-strain compressive behaviour and shows a significant dependence on pore size. [source]