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1
Starov, Victor, Anna Trybala, Phillip Johnson e Mauro Vaccaro. "Foam Quality of Foams Formed on Capillaries and Porous Media Systems". Colloids and Interfaces 5, n. 1 (8 febbraio 2021): 10. http://dx.doi.org/10.3390/colloids5010010.
Testo completoAbstract (sommario):
Foams are of great importance as a result of their expansive presence in everyday life—they are used in the food, cosmetic, and process industries, and in detergency, oil recovery, and firefighting. There is a little understanding of foam formation using soft porous media in terms of the quality of foam and foam formation. Interaction of foams with porous media has recently been investigated in a study by Arjmandi-Tash et al., where three different regimes of foam drainage in contact with porous media were observed. In this study, the amount of foam generated using porous media with surfactant solutions is investigated. The aim is to understand the quality of foam produced using porous media. The effect of capillary sizes and arrangement of porous in porous media has on the quality of foam is investigated. This is then followed by the use of soft porous media for foam formation to understand how the foam is generated on the surface of the porous media and the effect that different conditions (such as concentration) have on the quality of the foam. The quality of foam is a blanket term for bubble size, liquid volume fraction, and stability of the foam. The liquid volume fraction is calculated using a homemade dynamic foam analyser, which is used to obtain the distribution of liquid volume fraction along with the foam height. Soft porous media does not influence substantially the rate of decay of foam produced, however, it decreases the average diameter of the bubbles, whilst increasing the range of bubble sizes due to the wide range of pore sizes present in the soft porous media. The foam analyser showed the expected behaviour that, as the foam decays and becomes drier, the liquid volume fraction of the foam falls, and therefore the conductivity of foam also decreases, indicating the usefulness of the home-made device for future investigations.
2
Johnson, Phillip, Mauro Vaccaro, Victor Starov e Anna Trybala. "Foam Formation and Interaction with Porous Media". Coatings 10, n. 2 (5 febbraio 2020): 143. http://dx.doi.org/10.3390/coatings10020143.
Testo completoAbstract (sommario):
Foams are a common occurrence in many industries and many of these applications require the foam to interact with porous materials. For the first time interaction of foams with porous media has been investigated both experimentally and theoretically by O. Arjmandi-Tash et al. It was found that there are three different regimes of the drainage process for foams in contact with porous media: rapid, intermediate and slow imbibition. Foam formation using soft porous media has only been investigated recently, the foam was made using a compression device with soft porous media containing surfactant solution. During the investigation, it was found that the maximum amount of foam is produced when the concentration of the foaming agent (dishwashing surfactant) is in the range of 60–80% m/m. The amount of foam produced was independent of the pore size of the media in the investigated range of pore sizes. This study is expanded using sodium dodecyl sulphate (SDS), which has the same critical micelle concentration as the commercial dishwashing surfactant, where the foam is formed using the same porous media and compression device. During the investigation, it was found that 10 times the critical micelle concentration (CMC) is the optimum concentration for a pure SDS surfactant solution to create foam. Any further increase in concentration after that point resulted in no further mass of foam being generated.
3
Agbedor, Solomon-Oshioke, Donghui Yang, Jianqing Chen, Lei Wang e Hong Wu. "Low-Temperature Reactive Sintered Porous Mg-Al-Zn Alloy Foams". Metals 12, n. 4 (18 aprile 2022): 692. http://dx.doi.org/10.3390/met12040692.
Testo completoAbstract (sommario):
By using carbamide granules as the space holder, Mg alloy foams with interconnected pore structures were synthesized by reactive sintering of a mixture of Mg, Al and Zn powders. The effect of Zn/Al on the microstructural evolution and compressive strength of porous Mg-9Al-xZn (x = 1, 5) alloy foams was investigated. The phase diagram simulation approach was used to determine the sintering temperature. The analysis results show that the formation of binary secondary phases or intermetallic compounds is a crucial factor in achieving bonding strength for the porous Mg alloy foams. The intermetallic compounds were formed by solid-state diffusion between the metal powder elements. Mg17Al12 intermetallics was the most stable compound formed in the cell walls of porous Mg alloy foams. The addition of Zn influences the solubility and stability of the intermetallic compound. Thermodynamic calculations show that Mg17Al12 was preferentially formed in the cell walls owing to its high negative enthalpy energy. Moreover, various metastable transition phases may exist in the microstructures, especially in the porous Mg-9Al-5Zn alloy foam. The intermetallic phases act as reinforcing phases, combined with grain refinement, significantly increasing the strength of the foam. At the given relative density of 0.42, the porous Mg-9Al-5Zn alloy foam exhibits the highest yield strength of 9.0 MPa, which is 23% higher than the strength of the porous Mg-9Al-1Zn alloy foam.
4
Yamada, Yasuo, Takumi Banno, Yun Cang Li e Cui E. Wen. "Anisotropic Mechanical Properties of Nickel Foams Fabricated by Powder Metallurgy". Materials Science Forum 569 (gennaio 2008): 277–80. http://dx.doi.org/10.4028/www.scientific.net/msf.569.277.
Testo completoAbstract (sommario):
In the present study, porous nickel foam samples with pore sizes of 20 μm and 150 μm and porosities of 60 % and 70 % were fabricated by the space-holding sintering method via powder metallurgy. Electron scanning microscopy (SEM) and Image-Pro Plus were used to characterise the morphological features of the porous nickel foam samples. The anisotropic mechanical properties of porous nickel foams were investigated by compressive testing loading in different directions, i.e. the major pore axis and minor pore axis. Results indicated that the nominal stress of the nickel foam samples increases with the decreasing of the porosity. Moreover, the foam sample exhibited significantly higher nominal stress for loading in the direction of the major pore axis than loading in direction of the minor pore axis. It is also noticeable that the nominal stress of the nickel foams increases with the decreasing of the pore size. It seems that the deformation behaviour of the foams with a pore size in the micron-order differs from those with a macro-porous structure.
5
Shih, Albert J., e Zhenhua Huang. "Three-Dimensional Optical Measurements of Porous Foams". Journal of Manufacturing Science and Engineering 128, n. 4 (26 febbraio 2006): 951–59. http://dx.doi.org/10.1115/1.2194556.
Testo completoAbstract (sommario):
The optical, noncontact stereovision system and data analysis procedure are developed for the measurement of porous foams. The stereovision measurement system has demonstrated the capability to capture both the micro-scale features and the macro-scale shape of both the open-cell and closed-cell porous foams. A computational procedure, denoted as the grid method, is developed to identify representative planes on the porous foam surface using the stereovision measured data points. The relative positions between planes can be used to calculate the angles and distances between porous foam surfaces. A SiC open-cell and an aluminum closed-cell foams are used as examples to validate the grid method and demonstrate its computational efficiency. This research enables the form measurements and geometrical dimensioning and tolerancing of porous foams for quality control and assembly and contact analysis.
6
Douarche, Frederic, Benjamin Braconnier e Bernard Bourbiaux. "Foam placement for soil remediation: scaling foam flow models in heterogeneous porous media for a better improvement of sweep efficiency". Science and Technology for Energy Transition 78 (2023): 42. http://dx.doi.org/10.2516/stet/2023036.
Testo completoAbstract (sommario):
If injected with a large gas fraction, foam reduces mobility more in high-permeability layers and diverts flow to low-permeability layers. Here is a qualitative statement that has been claimed many times in many works related to environmental remediation and oil recovery. It is so true and relevant for foam flow in porous media and yet so little quantified and even less exploited in Darcy-scale numerical simulation. After briefly reviewing opportunities and challenges related to the use of foams in porous media and its Darcy-scale implicit-texture and population-balance modelling, we make a detour out of the strict framework of mathematical models by revisiting with a fresh eye the physics of foams on the large scale of heterogeneous natural porous media in terms of scaling laws. Specifically, it has been recently shown experimentally and theoretically that foam mobility reduction scales approximately as the square root of rock permeability within the framework of Darcy-type implicit-texture foam flow models [Douarche et al. (2020) Scaling foam flow models in heterogeneous reservoirs for a better improvement of sweep efficiency (Paper ThB04), in:17th European Conference of the Mathematics of Oil Recovery (ECMOR), Edinburgh, Scotland, 14–17 September; Gassara et al. (2020) Trans. Porous Media 131, 1, 193–221]. This also appears to hold for population-balance models under the local steady state assumption. This quantitative scaling law for the effect of permeability on foam properties was inferred from an analogy between foam flow in porous media and foam flow in capillary tubes and was found consistent with the modelling of available experimental data. We demonstrate by varying the permeability contrast and anisotropy of a stack of porous layers how foam regulates the flow and leads to flow diversion from high- to low-permeability layers. The threshold in permeability heterogeneity for which such a foam-driven diversion becomes effective is quantified through a sensitivity study accounting for foam injection type, permeability heterogeneity and anisotropy, heterogeneity structure, and scaling procedure. The simulations carried out clearly indicate that ignoring mobility reduction dependence on permeability in the foam process assessment of heterogeneous formations leads to an underestimation of mobility reduction benefits to improve flow conformance. The question of cores selection, as this rock-typing strategy in relation to the porous medium characterization may guide a smart and optimal design of pre-feasibility laboratory campaign for foam evaluation, and the generalization of the findings to multi-facies geological formations are also discussed. As such, the use of physical foam mobility reduction scaling law is highly recommended for foam process evaluation.
7
Wong, Pei-Chun, Sin-Mao Song, Pei-Hua Tsai, Muhammad Jauharul Maqnun, Wei-Ru Wang, Jia-Lin Wu e Shian-Ching (Jason) Jang. "Using Cu as a Spacer to Fabricate and Control the Porosity of Titanium Zirconium Based Bulk Metallic Glass Foams for Orthopedic Implant Applications". Materials 15, n. 5 (3 marzo 2022): 1887. http://dx.doi.org/10.3390/ma15051887.
Testo completoAbstract (sommario):
In this study, a porous titanium zirconium (TiZr)-based bulk metallic foam was successfully fabricated using the Cu spacer by employing the hot press method. TiZr-based bulk metallic foams with porosities ranging from 0% to 50% were fabricated and analyzed. The results indicate that thermal conductivity increased with the addition of Cu spacer; the increased thermal conductivity reduced the holding time in the hot press method. Moreover, the compressive strength decreased from 1261 to 76 MPa when the porosity of the TiZr-based bulk metallic foam increased to 50%, and the compressive strength was predictable. In addition, the foam demonstrated favorable biocompatibility in cell viability, cell migration capacity, and calcium deposition tests. Moreover, the pore size of the porous TiZr-based bulk metallic foam was around 120 µm. In conclusion, TiZr-based bulk metallic foam has favorable biocompatibility, mechanical property controllability, and porous structure for bone ingrowth and subsequent enhanced osteointegration. This porous TiZr-based bulk metallic foam has great potential as an orthopedic implant to enhance bone healing and decrease healing time.
8
Thanh, Tram Nguyen Xuan, Michito Maruta, Kanji Tsuru, Alireza Valanezhad, Shigeki Matsuya e Ishikawa Kunio. "Fabrication of Calcite Foam by Inverse Ceramic Foam Method". Key Engineering Materials 529-530 (novembre 2012): 153–56. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.153.
Testo completoAbstract (sommario):
We have previously reported that calcite foam that had interconnected porous structure could be prepared by ceramic foam method and it transformed to carbonate apatite (CO3Ap). In the ceramic foam method, polyurethane sponge was used as a template. The polyurethane sponge was immersed in the ceramics slurry, and the strut of the polyurethane foam was covered by ceramic powder. After that it was dried and sintered at high temperature. Calcite foams produced by this approach were comprised of a three-dimensional (3D) interconnected porous structure that facilitated cell penetration. However, all foams have a common limitation: the inherent lack of mechanical strength associated with high porosity. Therefore, in this study, an inverse ceramic foam method was studied; multi polyurethane coating method using polyurethane foam as a template. In this study, the compressive strength was improved by an inverse replication allowed for decreasing porosity while at the same time maintaining the interconnectivity. The burnable synthetic resin coating layer was introduced onto struts of polyurethane foam to make the triangular struts become more round and thick, consequently producing large round capillary within the foam structure fulfilling the requirement for osteoblast colonization. In particular, polyurethane foam was dipped orderly into two monomers, followed by centrifugation to remove excess liquids inside foam. After resin curing, a layer of synthetic resin was coated strut of foam. Calcium hydroxide Ca (OH)2 slurry was then infiltrated into resin coated-polyurethane foam. By firing at 600°C in O2-CO2 stream, polyurethane template was burnt off and Ca (OH)2 was converted into calcite. Negative replicated calcite foam was fabricated and characterized micro-structurally with interconnectivity and improved mechanical strength. The results obtained in this study suggested that this method dramatically improved the mechanical strength of the calcite foam without sacrificing the interconnected structure, and this means that the calcite foam obtained in this method could be precursors for the 3D interconnected porous CO3Ap foam.
9
Wong, Wai Yee, Ahmad Fauzi Mohd Noor e Radzali Othman. "Sintering of Beta-Tricalcium Phosphate Scaffold Using Polyurethane Template". Key Engineering Materials 694 (maggio 2016): 94–98. http://dx.doi.org/10.4028/www.scientific.net/kem.694.94.
Testo completoAbstract (sommario):
Porous beta-tricalcium phosphate (β-TCP) bioceramic has been reported as synthetic graft for cancellous bone substitute due to its biocompatibility and biodegradability properties. A highly porous and interconnected porosity architecture of bone scaffold facilitates attachment and in-growth of new bone tissue. β-TCP foam, a porous 3-dimensional scaffold was fabricated by employing polymeric foam replica method in this study. Polyurethane (PU) foam was used as the sacrificial template, in which β-TCP slurry with powder to water ratio of 10g:10ml was coated on PU template and sintered to 1100, 1200, 1250 and 1300°C. Observation on architecture of the foam, macrostructure and microstructure of pores and surface topography of porous strut showed that sintering at 1250°C produced sufficient densification of grains and micropores on the β-TCP strut. The β-TCP foams exhibited high porosity (92 – 97%) and large pore size (200 - 750um) that resemble cancellous bone structure.
10
Xiong, Jian Yu, Yun Cang Li, Yasuo Yamada, Peter D. Hodgson e Cui E. Wen. "Processing and Mechanical Properties of Porous Titanium-Niobium Shape Memory Alloy for Biomedical Applications". Materials Science Forum 561-565 (ottobre 2007): 1689–92. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.1689.
Testo completoAbstract (sommario):
Ti-26 at.%Nb (hereafter Ti-26Nb) alloy foams were fabricated by space-holder sintering process. The porous structures of the foams were characterized by scanning electron microscopy (SEM). The mechanical properties of the Ti-26Nb foam samples were investigated using compressive test. Results indicate that mechanical properties of Ti-26Nb foam samples are influenced by foam porosity. The plateau stresses and elastic moduli of the foams under compression decrease with the increase of their porosities. The plateau stresses and elastic moduli are measured to be from 10~200 MPa and 0.4~5.0 GPa for the Ti-26Nb foam samples with porosities ranged from 80~50 %, respectively.
11
Zhang, Xiaoyang, Liqun Tang, Zhenyu Jiang, Zejia Liu, Yiping Liu e Daining Fang. "Effects of Meso Shape Irregularity of Metal Foam on Yield Features under Triaxial Loading". International Journal of Structural Stability and Dynamics 15, n. 07 (31 agosto 2015): 1540014. http://dx.doi.org/10.1142/s0219455415400143.
Testo completoAbstract (sommario):
Metallic foam is a typical porous material with heterogeneous meso structures that affect the metallic foam's mechanical properties, in which shape irregularity of meso structures (porous cells) is the key. Shape irregularity of a porous cell reflects the deviation the cell shape from a sphere having the same volume. This paper examines the effects of meso shape irregularity of metallic foam on yield features based on three-dimensional (3D) Voronoi model and the finite element (FE) method. Three cubic foams designed by 3D Voronoi technique were constructed to furnish different statistics of shape irregularity but with the same initial density. Three normal stresses were applied on cubic metallic foam proportionally to implement the triaxial proportional loading in triaxial compression and tension. The yield surface of each 3D Voronoi foam under triaxial loading was calculated, and the influence of shape irregularity on the yield surface was investigated. The results show that the yield surface in (σe, σm) space may be depicted by an ellipse for metallic foams with different shape irregularities. The meso shape irregularity does clearly affect the yield surface with larger shape irregularity producing a smaller yield surface. This means that the metallic foam with larger shape irregularity yields more easily, and this feature is also reflected in the normalized yield surface for metallic foams with different irregularities.
12
Lagzdiņš, Aivars, Alberts Zilaucs, Ilze Beverte e Jānis Andersons. "Modeling the Nonlinear Deformation of Highly Porous Cellular Plastics Filled with Clay Nanoplatelets". Materials 15, n. 3 (28 gennaio 2022): 1033. http://dx.doi.org/10.3390/ma15031033.
Testo completoAbstract (sommario):
Rigid low-density plastic foams subjected to mechanical loads typically exhibit a nonlinear deformation stage preceding failure. At moderate strains, when the geometrical nonlinearity is negligible, such foam response is predominantly caused by the nonlinearity of deformation of their principal structural elements—foam struts. Orientational averaging of stresses in foam struts enables estimation of the stresses taken up by foams at a given applied strain. Based on a structural model of highly porous anisotropic cellular plastics filled with clay nanoplatelets and the orientational averaging, a method for calculating their nonlinear deformation is derived in terms of structural parameters of the porous material, the mechanical properties of the monolithic polymer, and filler particles and their spatial orientation. The method is applied to predicting the tensile stress-strain diagrams of organoclay-filled low-density rigid polyurethane foams, and reasonable agreement with experimental data is demonstrated.
13
Nikaido, Taro, Kanji Tsuru, Fumikazu Daitou, Melvin L. Munar, Shigeki Matsuya, Seiji Nakamura e Ishikawa Kunio. "Fabrication of βTCP with Fully-Interconnected Porous Structure". Key Engineering Materials 493-494 (ottobre 2011): 135–38. http://dx.doi.org/10.4028/www.scientific.net/kem.493-494.135.
Testo completoAbstract (sommario):
Calcium phosphate foam could be an ideal bone filler and scaffold for tissue engineering. This paper describes fabrication method of β-tricalcium phosphate (βTCP) foam with fully-interconnected porous structure by employing magnesium oxide (MgO) as βTCP stabilizer. The foam was prepared using the so-called ceramics foam method. MgO was added to calcium carbonate and dicalcium phosphate dihydrate so that 0, 1, 2, 3, 4, 6 and 8 mol% calcium would be substituted by magnesium (Mg) in βTCP structure. After sintering at 1500°C, crystal phase of the obtained foam included α-tricalcium phosphate (αTCP) when no Mgor less than 3 mol% Mg was added. In contrast, crystal phase was single phase βTCP when 3 mol% or higher Mg was added. The compressive strength was approximately 15 kPa and the porosity was above 95% for all specimens. No significant difference was observed between αTCP and βTCP foams in compressive strength and porosity when the sintering temperature was the same.
14
Antonini, Carlo, Tingting Wu, Tanja Zimmermann, Abderrahmane Kherbeche, Marie-Jean Thoraval, Gustav Nyström e Thomas Geiger. "Ultra-Porous Nanocellulose Foams: A Facile and Scalable Fabrication Approach". Nanomaterials 9, n. 8 (9 agosto 2019): 1142. http://dx.doi.org/10.3390/nano9081142.
Testo completoAbstract (sommario):
Cellulose nanofibril foams are cellulose-based porous materials with outstanding mechanical properties, resulting from the high strength-to-weight ratio of nanofibrils. Here we report the development of an optimized fabrication process for highly porous cellulose foams, based on a well-controlled freeze-thawing-drying (FTD) process at ambient pressure. This process enables the fabrication of foams with ultra-high porosity, up to 99.4%, density of 10 mg/cm3, and liquid (such as oil) absorption capacity of 100 L/kg. The proposed approach is based on the ice-templating of nanocellulose suspension in water, followed by thawing in ethanol and drying at environmental pressures. As such, the proposed fabrication route overcomes one of the major bottle-necks of the classical freeze-drying approach, by eliminating the energy-demanding vacuum drying step required to avoid wet foam collapse upon drying. As a result, the process is simple, environmentally friendly, and easily scalable. Details of the foam development fabrication process and functionalization are thoroughly discussed, highlighting the main parameters affecting the process, e.g., the concentration of nanocellulose and additives used to control the ice nucleation. The foams are also characterized by mechanical tests and oil absorption measurements, which are used to assess the foam absorption capability as well as the foam porosity. Compound water-in-oil drop impact experiments are used to demonstrate the potential of immiscible liquid separation using cellulose foams.
15
Kang, Yeon June, e J. Stuart Bolton. "Optimal Design of Acoustical Foam Treatments". Journal of Vibration and Acoustics 118, n. 3 (1 luglio 1996): 498–504. http://dx.doi.org/10.1115/1.2888212.
Testo completoAbstract (sommario):
A finite element model for elastic porous materials is presented that allows for interfaces with adjacent acoustical media that are arbitrarily oriented with respect to the global coordinate system. The foam finite element is based on a complete elastic porous material theory that can account for all the three wave types known to be significant in foams. Example problems are used to illustrate the application of foam finite elements to the optimal design of a foam wedge terminating a waveguide. The wedge angle is used as a design parameter (while the wedge volume is held constant) and the performance measure is the frequency-averaged absorption coefficient.
16
Hedayati, Reza, Alejandro Rubio Carpio, Salil Luesutthiviboon, Daniele Ragni, Francesco Avallone, Damiano Casalino e Sybrand van der Zwaag. "Role of Polymeric Coating on Metallic Foams to Control the Aeroacoustic Noise Reduction of Airfoils with Permeable Trailing Edges". Materials 12, n. 7 (2 aprile 2019): 1087. http://dx.doi.org/10.3390/ma12071087.
Testo completoAbstract (sommario):
Studies on porous trailing edges, manufactured with open-cell Ni-Cr-Al foams with sub-millimeter pore sizes, have shown encouraging results for the mitigation of turbulent boundary-layer trailing-edge noise. However, the achieved noise mitigation is typically dependent upon the pore geometry, which is fixed after manufacturing. In this study, a step to control the aeroacoustics effect of such porous trailing edges is taken, by applying a polymeric coating onto the internal foam structure. Using this method, the internal topology of the foam is maintained, but its permeability is significantly affected. This study opens a new possibility of aeroacoustic control, since the polymeric coatings are temperature responsive, and their thickness can be controlled inside the foam. Porous metallic foams with pore sizes of 580, 800, and 1200 μm are (internally) spray-coated with an elastomeric coating. The uncoated and coated foams are characterized in terms of reduced porosity, average coating thickness and air-flow resistance. Subsequently, the coated and uncoated foams are employed to construct tapered inserts installed at the trailing edge of an NACA 0018 airfoil. The noise mitigation performances of the coated metal foams are compared to those of uncoated metal foams with either similar pore size or permeability value, and both are compared to the solid trailing edge reference case. Results show that that the permeability of the foam can be easily altered by the application of an internal coating on the metallic foams. The noise reduction characteristics of the coated foams are similar to equivalent ones with metallic materials, provided that the coating material is rigid enough not to plastically deform under flow conditions.
17
Kotresha, Banjara, e Nagarajan Gnanasekaran. "Comparison of Fluid Flow and Heat Transfer Through Metal Foams and Wire Mesh by Using CFD". Recent Patents on Mechanical Engineering 12, n. 3 (26 settembre 2019): 220–26. http://dx.doi.org/10.2174/2212797612666190717163207.
Testo completoAbstract (sommario):
Background: The unique structural characteristics of the metal foams, such as low density, large surface area, ability to increase turbulence, and increased heat transfer efficiency, are the advantages associated with thermal applications such as electronics cooling, refrigeration air conditioning, etc. The porous metal foam structures are extensively used to enhance heat transfer. Objective: This paper discusses the numerical simulations of a vertical channel filled with metal foam and wire mesh. The fluid flow and heat transfer phenomena of a wire mesh are compared with two different types of metal foams. Metal foams are made of aluminium and copper while the wire mesh is made of brass. The porosity of the metallic porous structures varies from 0.85 to 0.95. Methods: A Darcy extended Forchheirmer model is considered for solving fluid flow through the porous media while the heat transfer through the porous media is predicted using local thermal non-equilibrium model. Results: Initially, the results obtained using the proposed numerical procedures are compared with experimental results available in the literature. The numerical simulations suggest that the pressure drop increases as the velocity of the fluid increases and decreases as the porosity increases. The heat transfer coefficient and Nusselt number are determined for both the metal foams and the wire mesh. Conclusion: The Nusselt number obtained for wire mesh shows almost 90% of the copper metal foam in the same porosity range. The numerical results suggest that the brass wire mesh porous medium can also be used for enhancement of heat transfer. In this article, patents have been discussed.
18
Singh, Robin, e Kishore K. Mohanty. "Foams Stabilized by In-Situ Surface-Activated Nanoparticles in Bulk and Porous Media". SPE Journal 21, n. 01 (18 febbraio 2016): 121–30. http://dx.doi.org/10.2118/170942-pa.
Testo completoAbstract (sommario):
Summary Foams for subsurface applications are traditionally stabilized by surfactants. The goal of this work is to study foam stabilization by nanoparticles—in particular, by in-situ surface-hydrophobization of hydrophilic nanoparticles. The interfacial properties of the nanoparticles were modulated by the attachment of short-chain surface modifiers (alkyl gallates) that render them partially hydrophobic, but still fully dispersible in water. First, static foams were generated with nanoparticles with varying concentrations of surface modifiers. The decay of foam height with time was measured, and half-lives were determined. Optical micrographs of foam stabilized by surface-modified nanoparticles (SMNPs) and surfactant were recorded. Second, aqueous foams were created in-situ by coinjecting the SMNP solutions with nitrogen gas through a Berea sandstone core at a fixed quality. Pressure drop across the core was measured to estimate the achieved resistance factor. These pressure-drop results were then compared with those of a typical surfactant (alpha olefin sulfonate, alkyl polyglucoside) under similar conditions. Finally, oil-displacement experiments were conducted in Berea cores with surfactant and SMNP solutions as foaming agents (coinjection with nitrogen gas). A Bartsch shake test revealed the strong foaming tendency of SMNPs even with a very low initial surface-modifier concentration (0.05 wt%), whereas hydrophilic nanoparticles alone could not stabilize foam. The bubble texture of foam stabilized by SMNPs was finer than that with surfactants, indicating a stronger foam. As the degree of surface coating increased, the resistance factor of SMNP foam in a Berea core increased significantly. The corefloods in the sandstone cores with a reservoir crude oil showed that immiscible foams with SMNP solution can recover a significant amount of oil (20.6% of original oil in place) over waterfloods.
19
Sharma, Shyam, Rahul Khatri e Anurag Joshi. "A synergistic approach to the development of lightweight aluminium-based porous metallic foam using stir casting method". Metal Working and Material Science 25, n. 4 (11 dicembre 2023): 255–67. http://dx.doi.org/10.17212/1994-6309-2023-25.4-255-267.
Testo completoAbstract (sommario):
Introduction. A synergetic approach to the development of lightweight aluminium metal foam by stir casting process is presented and various mechanical properties and microstructure are tested. The purpose of this study is due to the constant industrial demand for lightweight materials and increased research interest in porous substrates, mainly due to its unique properties. Materials and method. The method used for developing metallic aluminium foam was stir casting with calcium carbonate as a foaming agent to achieve a target interconnected porous microenvironment on a metal foam substrate. Results and Discussion. A set of physical properties, such as apparent density (1.8 g/cm3), relative density (0.67 g/cm3) and porosity (30%) of the developed aluminium-based metal foams, is stated as the result. The developed metal foam has a strength-to-weight ratio 67% higher than that of the base material. In addition, the results of field emission scanning electron microscopy of the developed metal foam confirm the presence of a porous network with a pore size from 0.075 mm to 1.43 mm. Energy dispersive spectroscopy confirmed the presence of the desired elements with minimal contamination in the developed aluminium foam substrates. Metal foam demonstrates a higher compressive strength (607 kN) compared to the base metal (497 kN). The mechanical characteristics of the developed metal foam substrate (hardness, compressive strength and impact energy) show the expected results compared to the base material. In general, the developed aluminium foam substrate established a promising route to the development of highly performance lightweight metal foam for shock absorber and acoustic applications.
20
Koponen, Antti I., Oleg Timofeev, Ari Jäsberg e Harri Kiiskinen. "Drainage of high-consistency fiber-laden aqueous foams". Cellulose 27, n. 16 (11 settembre 2020): 9637–52. http://dx.doi.org/10.1007/s10570-020-03416-y.
Testo completoAbstract (sommario):
AbstractLightweight lignocellulosic fibrous materials (LLFMs) offer a sustainable and biodegradable alternative in many applications. Enthusiastic interest in these materials has recently grown together with the newly risen interest in foam forming. Foam bubbles restrain fiber flocculation, and foam formed structures have high uniformity. Moreover, the bubbles support the fibrous structure during manufacturing enabling the formation of highly porous structures. Mechanical pressure cannot be applied in the manufacture of LLFMs as the materials would lose their porous structure. Water is therefore typically removed by a combination of drainage and thermal drying. Thermal drying of porous materials has been studied intensively. However, there are only a few studies on the drainage of fiber-laden foams. Thus, in this work, we conducted a systematic analysis of this topic. Our findings show that after drainage a stationary vertical moisture profile similar to that of pure foams is developed. Raising the initial fiber consistency was found to increase the final fiber consistency of the foam until the drainage ceased. Increasing mold height was found to increase the final consistency considerably. Without vacuum and heating, the shrinkage of samples during drainage was only slightly higher than the volume of the drained water. Drainage rate and final consistency increased clearly with increasing vacuum, but simultaneously sample shrinkage increased considerably. The best compromise was obtained with a vacuum of 0.5 kPa, which increased the final consistency by 60% without extra shrinkage. Using warm foam and heating the foam during drainage increased the final consistency considerably, but this also led to significant shrinkage of the sample.
21
Yasmin, Y., M. N. Mazlee, A. H. Norzilah, J. B. Shamsul, Rahmat Azmi, W. H. Chan e Hazrin Jahidi. "The Development and Characterisation of Porous Clay - Precipitated Calcium Carbonate". Key Engineering Materials 694 (maggio 2016): 189–94. http://dx.doi.org/10.4028/www.scientific.net/kem.694.189.
Testo completoAbstract (sommario):
Ceramic foams, a porous material with a gyroid structures, are becoming highly demanded for various applications such as heat insulation, bone implantation and filtration, because of their unique properties such as high specific surface area, high porosity and low heat transfer rate. In this study, the development of ceramic foam utilised white clay with a combination of precipitated calcium carbonate (PCC). The ceramic foam was successfully developed using this combination after the sample was sintered at 1250 °C for 2 hours holding time. The various compositions of PCC (10.0, 12.5, 15.0, 17.5, 20.0, 22.5 and 25.0 wt.%) affected the chemical composition and compressive strength of the ceramic foam. The chemical composition of ceramic foam was analysed by using X -ray fluorescence (XRF) and the result indicated that the PCC was successfully transformed into calcium oxide (CaO) after the sintering process. The mineralogical composition of the ceramic foam was evaluated using X-ray diffraction (XRD) and has shown the presence of mullite (3Al2O3.2SiO2), gehlenite (Ca2Al2SiO7) and anorthite (2CaAl2Si2O8) after the sintering process. The scanning electron microscope (SEM) analysis showed that the presence of porosity on the strut of the ceramic foam. Meanwhile, the compressive strength of the ceramic foam increased from 0.03 to 1.31 MPa, which is directly proportional to the increased amount of PCC.
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Manetti, L. L., A. S. Moita e E. M. Cardoso. "Thermal efficiency of metal foams on pool boiling". Journal of Physics: Conference Series 2116, n. 1 (1 novembre 2021): 012005. http://dx.doi.org/10.1088/1742-6596/2116/1/012005.
Testo completoAbstract (sommario):
Abstract This paper presents an experimental work on pool boiling using HFE-7100 at saturated conditions, under atmospheric pressure, and copper and nickel foams as the heating surface with four different thicknesses varying between 0.5 mm and 3 mm, followed by an analysis of the effect of foam fin-efficiency based on Ghosh model. All foams showed a better heat transfer coefficient (HTC) than the plain surface; however, as the heat flux increased, the HTC from the thicker nickel foams decreased due to the bubble vapor flow inside the foam. On the other hand, the thinner nickel foam showed better HTC at high heat fluxes with a maximum enhancement of 120%. The foam efficiency presented a similar tendency with the HTC, i.e., as the thickness decreases the efficiency increases; however, as compared with copper foams with a similar area but different porous diameter, the copper foams are 40% more efficient than the nickel ones due to the foam material, which has a thermal conductivity 4.5 times higher.
23
Jang, Hyesoo, Myoung-Hwan Kim, Sang-Kyun Park, Yul-Seong Kim e Byung Chul Choi. "Simulation of Heat and Mass Transfer Characteristics for the Optimal Operating Conditions of a Gas-to-Gas Membrane Humidifier with Porous Metal Foam". Energies 13, n. 19 (1 ottobre 2020): 5110. http://dx.doi.org/10.3390/en13195110.
Testo completoAbstract (sommario):
The shell-and-tube type gas-to-gas membrane humidifier used with air supply to polymer electrolyte membrane fuel cell supplies heat and vapor through a membrane and does not require an additional power source. Packing porous metal foam in the flow path of the membrane humidifier can result in higher heat and mass transfer efficiencies due to heat conduction through metal. In this study, the influence of various operating conditions and types of porous metal foams on the transport characteristics of the membrane humidifier are evaluated by simulation. The main factor causing the improvement of heat and mass transfer is the high conductivity of the porous metal foam, which is significantly correlated with the type of material used, compression ratio, and pore diameter. Additionally, the heat and mass transfer changes significantly when the flow velocity and channel size change due to the effect of the metal foam becoming more pronounced.
24
Li, Ying Ge, Dian Cai Geng, Fa Hu Zhang e Dong Xing Du. "Proper Index of Foam Statics Characteristics on Predicting Foam Dynamics Behavior in Porous Media". Key Engineering Materials 561 (luglio 2013): 411–16. http://dx.doi.org/10.4028/www.scientific.net/kem.561.411.
Testo completoAbstract (sommario):
Proper foam statics index can give essential indications on foam dynamic behavior in porous media. In this paper, the statics characteristics are investigated through air-flow method for foam generated with Sodium Dodecyl Sulfate (SDS) surfactant. Parameters of foam height, foam half period time are recorded for various gas phases, surfactant concentrations and injecting gas flow rate, and foam morphology are also visually monitored. It is found the N2 generated foam has better characteristics on foam height, while poorer characteristics on foam half-time period compared to air and CO2 foam. Widely employed Foam Composite Index (FCI) is no longer suitable for predicting foam dynamic behavior, a Foam Index for predicting Dynamic Behavior in Porous Media (FIDBPM) is therefore defined to predict properly the foam transient propagation process in porous media.
25
Werner, David, Johanna Maier, Nils Kaube, Vinzenz Geske, Thomas Behnisch, Matthias Ahlhelm, Tassilo Moritz, Alexander Michaelis e Maik Gude. "Tailoring of Hierarchical Porous Freeze Foam Structures". Materials 15, n. 3 (22 gennaio 2022): 836. http://dx.doi.org/10.3390/ma15030836.
Testo completoAbstract (sommario):
Freeze foaming is a method to manufacture cellular ceramic scaffolds with a hierarchical porous structure. These so-called freeze foams are predestined for the use as bone replacement material because of their internal bone-like structure and biocompatibility. On the one hand, they consist of macrostructural foam cells which are formed by the expansion of gas inside the starting suspension. On the other hand, a porous microstructure inside the foam struts is formed during freezing and subsequent freeze drying of the foamed suspension. The aim of this work is to investigate for the first time the formation of macrostructure and microstructure separately depending on the composition of the suspension and the pressure reduction rate, by means of appropriate characterization methods for the different pore size ranges. Moreover, the foaming behavior itself was characterized by in-situ radiographical and computed tomography (CT) evaluation. As a result, it could be shown that it is possible to tune the macro- and microstructure separately with porosities of 49–74% related to the foam cells and 10–37% inside the struts.
26
Leong, K. C., L. W. Jin, I. Pranoto, H. Y. Li e J. C. Chai. "Experimental Study of Enhanced Pool Boiling Heat Transfer Using Graphite Foam Inserts". Defect and Diffusion Forum 312-315 (aprile 2011): 352–57. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.352.
Testo completoAbstract (sommario):
This paper presents the results of an experimental study of heat transfer in a pool boiling evaporator with porous insert. Different types of graphite foams were tested with the phase change coolant FC-72 in a designed thermosyphon. Comparisons between the graphite foams and a solid copper block show that the porous structure enhances pool boiling significantly. The boiling thermal resistance of the tested graphite foams was found to be about 2 times lower than that of the copper block. The bubble formation recorded by a high speed camera indicates that boiling from a graphite foam is more vigorous than from a copper block. The designed thermosyphon with graphite foam insert can remove heat fluxes of up to 112 W/cm2 with the maximum heater temperature maintained below 100°C.
27
Koursari, Nektaria, Omid Arjmandi-Tash, Phillip Johnson, Anna Trybala e Victor M. Starov. "Foam drainage placed on a thin porous layer". Soft Matter 15, n. 26 (2019): 5331–44. http://dx.doi.org/10.1039/c8sm02559b.
Testo completoAbstract (sommario):
A theory of foam drainage placed on thin porous layer is developed. The rate of foam drainage and imbibition inside the porous layer and the possibility of a build-up of a free liquid layer on the foam/porous layer interface are investigated.
28
Huang, Yao, Zexin Li, Lucai Wang, Leilei Sun, Xiaohong You, Wenzhan Huang e Fang Wang. "Preparation and Heat Dissipation Properties Comparison of Al and Cu Foam". Metals 12, n. 12 (30 novembre 2022): 2066. http://dx.doi.org/10.3390/met12122066.
Testo completoAbstract (sommario):
The space holder method, a kind of powder metallurgy method which can avoid the process of melting metal to prepare metal foams, has particular significance in solving the difficulty of preparing metal foams with high melting points. In this paper, Na2S2O3·5H2O, a novel space holder, was used to prepare aluminium foam and copper foam, which were then used to test the heat dissipation performance of the metal foams. We first prepared two kinds of cell structures for (spherical cell and composite cells) aluminium and copper foam, then, we compared the performances of their heat dissipation, and it was found that both the spherical cell metal foam and composite cell metal foam promoted heat dissipation in the environment of natural convection, and the difference between them was not apparent. In the environment of forced convection, the composite porous metal showed a better heat dissipation performance.
29
Seciureanu, Mihai, Silviu-Marian Nastac, Maria-Violeta Guiman e Petronela Nechita. "Cellulose Fibers-Based Porous Lightweight Foams for Noise Insulation". Polymers 15, n. 18 (17 settembre 2023): 3796. http://dx.doi.org/10.3390/polym15183796.
Testo completoAbstract (sommario):
This paper examines effective and environmentally friendly materials intended for noise insulation and soundproofing applications, starting with materials that have gained significant attention within last years. Foam-formed materials based on cellulose fibers have emerged as a promising solution. The aim of this study was to obtain a set of foam-formed, porous, lightweight materials based on cellulose fibers from a resinous slurry pulp source, and to investigate the impact of surfactant percentage of the foam mixtures on their noise insulation characterisitcs. The basic foam-forming technique was used for sample assembly, with three percentages of sodium dodecyl sulphate (as anionic surfactant) related to fiber weight, and a standardised sound transmission loss tube procedure was used to evaluate noise insulation performance. Results were obtained as observations of internal structural configurations and material characteristics, and as measurements of sound absorption/reflection, sound transmission loss, and surface acoustic impedance. Based on the findings within this study, the conclusions highlight the strong potential of these cellulosic foams to replace widely used synthetic materials, at least into the area of practical noise insulation applications.
30
Dukhan, Nihad. "Equivalent Parallel Strands Modeling of Highly-Porous Media for Two-Dimensional Heat Transfer: Application to Metal Foam". Energies 14, n. 19 (2 ottobre 2021): 6308. http://dx.doi.org/10.3390/en14196308.
Testo completoAbstract (sommario):
A new geometric modeling of isotropic highly-porous cellular media, e.g., open-cell metal, ceramic, and graphite foams, is developed. The modelling is valid strictly for macroscopically two-dimensional heat transfer due to the fluid flow in highly-porous media. Unlike the current geometrical modelling of such media, the current model employs simple geometry, and is derived from equivalency conditions that are imposed on the model’s geometry a priori, in order to ensure that the model produces the same pressure drop and heat transfer as the porous medium it represents. The model embodies the internal structure of the highly-porous media, e.g., metal foam, using equivalent parallel strands (EPS), which are rods arranged in a spatially periodic two-dimensional pattern. The dimensions of these strands and their arrangement are derived from equivalency conditions, ensuring that the porosity and the surface area density of the model and of the foam are indeed equal. In order to obtain the pressure drop and heat transfer results, the governing equations are solved on the geometrically-simple EPS model, instead of the complex structure of the foam. By virtue of the simple geometry of parallel strands, huge savings on computational time and cost are realized. The application of the modeling approach to metal foam is provided. It shows how an EPS model is obtained from an actual metal foam with known morphology. Predictions of the model are compared to experimental data on metal foam from the literature. The predicted local temperatures of the model are found to be in very good agreement with their experimental counterparts, with a maximum error of less than 11%. The pressure drop in the model follows the Forchheimer equation.
31
Xie, Rujia, Zhenxing Fang, Jiefeng Yan, Wei Wang, Xuan Cao e Xiaoyang Qiu. "Fabrication of diverse carbon forms and their reversed applications in hexane/water separation". Water Science and Technology 82, n. 7 (24 agosto 2020): 1296–303. http://dx.doi.org/10.2166/wst.2020.401.
Testo completoAbstract (sommario):
Abstract Melamine foam is an important material in production and life. A series of porous carbon foams were obtained through a simple carbonization process of melamine foam at different temperatures. The carbon foams obtained at the carbonization temperature of 400 and 600 °C reveal a hydrophobic and even super-hydrophobic property (water contact angle larger than 150°) with a hexane adsorption much larger than that of melamine foam. However, the carbon foam obtained at the carbonization temperature of 800 °C reveals a super-hydrophilic property (water contact angle smaller than 5°) due to its severest shrinkage during the carbonization process. Interestingly, this series of carbon foams have an excellent performance in oil adsorption. However, the carbon membranes derived from the 800 °C carbon foam reveals oleophobicity under water (the adsorbed water at the surface was extremely important), which allows the penetration of water and blocks the infiltration of hexane at the same time. These different carbon forms have reversed applications in hexane/water separation.
32
Pinto, Javier, Suset Barroso-Solares, Davide Magrì, Francisco Palazon, Simone Lauciello, Athanassia Athanassiou e Despina Fragouli. "Melamine Foams Decorated with In-Situ Synthesized Gold and Palladium Nanoparticles". Polymers 12, n. 4 (17 aprile 2020): 934. http://dx.doi.org/10.3390/polym12040934.
Testo completoAbstract (sommario):
A versatile and straightforward route to produce polymer foams with functional surface through their decoration with gold and palladium nanoparticles is proposed. Melamine foams, used as polymeric porous substrates, are first covered with a uniform coating of polydimethylsiloxane, thin enough to assure the preservation of their original porous structure. The polydimethylsiloxane layer allows the facile in-situ formation of metallic Au and Pd nanoparticles with sizes of tens of nanometers directly on the surface of the struts of the foam by the direct immersion of the foams into gold or palladium precursor solutions. The effect of the gold and palladium precursor concentration, as well as the reaction time with the foams, to the amount and sizes of the nanoparticles synthesized on the foams, was studied and the ideal conditions for an optimized functionalization were defined. Gold and palladium contents of about 1 wt.% were achieved, while the nanoparticles were proven to be stably adhered to the foam, avoiding potential risks related to their accidental release.
33
Jang, Lindy K., Landon D. Nash, Grace K. Fletcher, Thomas Cheung, Andrew Soewito e Duncan J. Maitland. "Enhanced X-ray Visibility of Shape Memory Polymer Foam Using Iodine Motifs and Tantalum Microparticles". Journal of Composites Science 5, n. 1 (6 gennaio 2021): 14. http://dx.doi.org/10.3390/jcs5010014.
Testo completoAbstract (sommario):
Shape memory polymer (SMP) foams are porous materials with high surface area and large volumetric expansion capabilities that are well suited for endovascular occlusion applications, including brain aneurysm embolization. However, many polyurethane SMP foams are inherently radiolucent when X-ray visibility is required to ensure the safe delivery of the foam to the targeted aneurysm site using fluoroscopy. Here, highly radio-dense tantalum microparticles were added to a previously reported triiodobenzene-containing SMP foam (ATIPA foam) premix to fabricate ATIPA foam-tantalum composites (AT_T). The AT_T foams showed comparable glass transition temperatures, faster expansion profiles, increased X-ray visibility, good cytocompatibility, and faster oxidative degradation compared to the control ATIPA foam without tantalum. The mechanical properties were improved up to 4 vol% tantalum and the X-ray visibility was most appropriate for the 2 vol% (AT_2%T) and 4 vol% (AT_4%T) tantalum foams. E-beam sterilization did not impair the critical properties of the ATIPA foams. Overall, AT_2%T was the optimal foam composition for neurovascular prototypes due to its high oxidative stability in vitro compared to previous low-density SMP foams. The AT_T foams are very promising materials with high toughness and sufficient X-ray visibility for use as neurovascular embolization devices.
34
Hsu, Y. H., I. G. Turner e A. W. Miles. "Fabrication of Porous Calcium Phosphate Bioceramics as Synthetic Cortical Bone Graft". Key Engineering Materials 284-286 (aprile 2005): 305–8. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.305.
Testo completoAbstract (sommario):
The aim of this study was to fabricate porous Hydroxyapatite/Tricalcium phosphate (HA/TCP) bioceramics with an adequate degree of interconnected porosity combined with optimal mechanical properties. Porous HA/TCP bioceramics with interconnected porosity and the controlled pore sizes necessary to simulate natural bone tissue morphology were fabricated by a novel technique of vacuum impregnation of reticulated polymeric foams with ceramic slip. By varying the characteristics of the slips and using foams of different pores per inch (ppi), samples of porous HA/TCP, blocks and granules, with a wide range of pore sizes were successfully manufactured. Functionally gradient materials (FGM) with porosity gradients were also made and no weakness was found at the interface. The pore size of the HA/TCP bioceramics was in the range of 197 – 254 µm (for 20 ppi foam), 143 – 182 µm (for 30 ppi foam) and 105 – 127 µm (for 45 ppi foam). The compressive strengths and the apparent densities of the HA/TCP samples were in the range of 30 –170 MPa and 2.34 – 2.76 g/cm3 respectively. These results indicate that it is possible to manufacture open pore HA/TCP bioceramics with compressive strengths comparable to human bone which could be of clinical interest.
35
Wadi, Vijay S., Kishore K. Jena, Shahrukh Z. Khawaja, Vengatesan Muthukumarswamy Ranagraj e Saeed M. Alhassan. "Preparation and processing of porous sulfur foams having low thermal conductivity". RSC Advances 9, n. 8 (2019): 4397–403. http://dx.doi.org/10.1039/c8ra09127g.
Testo completoAbstract (sommario):
Porous sulfur foams were prepared by combining inverse vulcanization and template removal techniques. The porosity of the foam was altered by varying the template particle size; which lead to drop in thermal conductivity.
36
Wang, Xiaoguang, Wei Li, Dehua Xiong e Lifeng Liu. "Fast fabrication of self-supported porous nickel phosphide foam for efficient, durable oxygen evolution and overall water splitting". Journal of Materials Chemistry A 4, n. 15 (2016): 5639–46. http://dx.doi.org/10.1039/c5ta10317g.
Testo completoAbstract (sommario):
Self-supported porous Ni–P foam is fabricated by a convenient one-step method, and exhibits excellent electrocatalytic performance towards oxygen evolution reaction. An alkaline electrolyzer constructed using two self-supported porous Ni–P foams shows superior energy efficiency of 90.2% at 10 mA cm−2, and can sustain 1000 h under operation conditions without obvious degradation.
37
Sirikulchaikij, Sanit, Benjaporn Nooklay, Rungrote Kokoo e Matthana Khangkhamano. "Rubber Foam Processing via Bubbling Technique". Materials Science Forum 962 (luglio 2019): 96–100. http://dx.doi.org/10.4028/www.scientific.net/msf.962.96.
Testo completoAbstract (sommario):
Natural rubber foams are currently produced by the two well-known processes of Dunlop and Talalay. Dunlop process, however, requires a high-speed Hobart Mixer to generate a high bubble-volume, while Talalay is complexity and expensive technique. Here, a simple and inexpensive technique for rubber foam production was introduced. The process involved air flowing with a constant flow rate through a porous diffuser, firmly connected to the bubble column containing compound latex, to generate a high bubble-volume. Microstructure of the as-produced rubber foams was examined using a scanning electron microscope (SEM), in comparison with that of the purchased Dunlop foam. Spherical cell shape with a uniform interconnected-cell structure was gained from the bubbled foams, while fractured-cell structure was obtained from the Dunlop foam.
38
Righetti, G., C. Zilio, G. Savio, R. Meneghello, M. Calati e S. Mancin. "Experimental pressure drops during the water flow into porous materials realized via additive manufacturing". Journal of Physics: Conference Series 2116, n. 1 (1 novembre 2021): 012059. http://dx.doi.org/10.1088/1742-6596/2116/1/012059.
Testo completoAbstract (sommario):
Abstract Open-cell foams offer several interesting possibilities in numerous technological fields. In fact, they present high surface area to volume ratio as well as enhanced flow mixing and attractive stiffness and strength. However, their complete and reliable characterization has not been completed yet. In fact, there is still no a comprehensive work that relates all the foam geometrical characteristics to their heat transfer and pressure drop features. This paper is the very first outcome of a larger study that aims at realizing open-cell foams via additive manufacturing, testing them, then generating a simulation model based on the real geometries to numerically optimize each parameter. The present manuscript presents the construction of the open-foam via 3D printing and the experimental pressure drop measurements when water flows through the foam.
39
Zhu, Qing You, Weike Peng, Cheng Ji Deng e Hong Xi Zhu. "The Preparation of Porous Andalusite Refractory by Foaming Method". Advanced Materials Research 881-883 (gennaio 2014): 1026–30. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.1026.
Testo completoAbstract (sommario):
Andalusite can be used to produce porous refractory with the method of foaming and its properties are very good. The bulk density can be controlled by the quantity of foam easily. The compressive strength can reach almost 9 Mpa (1.0g/cm3). The expansion transmit by pores, the remianing andalusite and the transverse growing of mullite crystal are all good for the stabilization of sample during heating. The agglomeration of foam is bad for foaming slurry while stiring, so one way to well-distribute the pores is enhancing the strength of foams. Andalusite can prolong the lifetime of refractory.
40
Krčmářová, Nela, Jan Šleichrt, Tomáš Doktor, Daniel Kytýř e Ondřej Jiroušek. "SEMI–AUTOMATED ASSESSMENT OF MICROMECHANICAL PROPERTIES OF THE METAL FOAMS ON THE CELL-WALL LEVEL". Acta Polytechnica CTU Proceedings 7 (9 dicembre 2016): 72. http://dx.doi.org/10.14311/app.2017.7.0072.
Testo completoAbstract (sommario):
Metal foams are innovative porous material used for wide range of application such as deformation energy or sound absorption, filter material, or microbiological incubation carrier. To predict mechanical properties of the metal foam is necessary to precisely describe elasto–plastic properties of the foam on cell–wall level. Indentation with low load is suitable tool for this purpose. In this paper custom designed instrumented microindentation device was used for measurement of cell-wall characteristics of two different aluminium foams (ALPORAS and ALCORAS). To demonstrate the possibility of automated statistical estimation of measured characteristics the device had been enhanced by semi-automatic indent positioning and evaluation procedures based on user-defined grid. Vickers hardness was measured on two samples made from ALPORAS aluminium foam and one sample from ALCORAS aluminium foam. Average Vickers hardness of ALPORAS foam was 24.465HV1.019 and average Vickers hardness of ALCORAS was 36.585HV1.019.
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Ranito, Cláudia M. S., Fernando A. Costa Oliveira e João P. Borges. "Hydroxyapatite Foams for Bone Replacement". Key Engineering Materials 284-286 (aprile 2005): 341–44. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.341.
Testo completoAbstract (sommario):
Hydroxyapatite, often in the form of synthetic porous blocks, has been used in the repair of bone defects for over 20 years owing to its biocompatibility and osseoconductive behaviour. Bone ingrowth requires the existence of open and interconnected pores with diameters larger than 150 µm for proper circulation of nutrients. Hence, currently available materials are characterised by poor mechanical properties. Collapse of such products is therefore a major source of concern to surgeons using these weak materials in bone surgery. There is a need to develop stronger highly porous structures through adequate control over the size, shape and volume fraction of pores. In this work, highly porous open-cell hydroxyapatite foams were fabricated by the polymer foam replication process, where two types of polyurethane (PU) foams were infiltrated with optimised slurries containing appropriate binders and ceramic particles, followed by the removal of excess slurry, burning out of the polymer to leave a ceramic replica of the polyurethane and finally high temperature sintering. Open-cell HAP foams with porosities of about 80% were obtained, i.e. 30% higher than that determined for commercial ones (50%). Many of the commercial foam cells approach 500 µm in diameter whereas the developed foam cell size ranged from 300 up to 500 µm. The ultimate compressive strength of the developed foams (1-2 MPa) was found to be higher than that recorded for the commercial ones (0.7 MPa) indicating that these foams can more easily be modelled in theatre. Both the elastic moduli and the compressive strength of the developed foams were found to increase with increasing of the relative density, in accordance with the predictions of available micro-mechanical models.
42
Ribeiro, Christiane, José Carlos Bressiani e Ana Helena A. Bressiani. "Obtention of TCP Porous Ceramic Using Albumin". Materials Science Forum 530-531 (novembre 2006): 587–92. http://dx.doi.org/10.4028/www.scientific.net/msf.530-531.587.
Testo completoAbstract (sommario):
In the last years, the porosity in ceramic materials for implants production has motivated the development of various technologies. Calcium phosphate ceramics, in special the tricalcium phosphate - TCP, are very promising as bone substitutes and scaffolds for tissue engineering. The macroporosity incorporation in TCP ceramics by porogenic, foaming and consolidator agent, as globular protein (ovalbumin) was the focus of this work. Preliminary studies of zeta potential were made to have a suitable suspension. Ovalbumin amounts (5-7 wt%) were added to the ceramic slurries and suspensions with a solid percentage higher than 60 wt% were obtained. The interaction albumin/surfactant with detergency properties was evaluated by pH and viscosity measurements. The foam was produced by mechanical stirring. The results suggested that the presence of the surfactant increase the volume and stability of foam. After drying, burnout and sintering (1200oC/30 min.) the phase composition of the foams was determined by X-ray diffraction. The microstructure and porosity were evaluated by scanning electron microscopy. SEM micrographs of the foam show that the structure consists of a permeable porous network, being observed spherical and interconnected pores.
43
Myalski, Jerzy, Bartosz Hekner e Andrzej Posmyk. "The influence of glassy carbon on tribological properties in metal – ceramic composites with skeleton reinforcement". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2015, CICMT (1 settembre 2015): 000121–24. http://dx.doi.org/10.4071/cicmt-tp44.
Testo completoAbstract (sommario):
This paper presents a results of mechanical and tribological properties of aluminum based composites with skeleton reinforcement. The aluminum alloy based composites were produced using pressure infiltration process. As a reinforcement ceramic foam with opened cells was applied. This reinforcement structure give an opportunity to limit the most common defects (like agglomeration, inhomogeneity, ect.) occurring in composite materials obtained by casting. In presented research three different types of porous foam were analysed. There were alumina foam covered by thin glassy carbon layer (Al2O3 – GC) and two types of glassy carbon foams (GC). Due to application of porous ceramic foam, an increasing of composite mechanical properties are expected. An additional glassy carbon layer with thickness up to 5 μm was applied for increasing a thermal conductivity and rapid heat dissipation from the material. Moreover, the skeleton structure of glassy carbon, and its wear mechanism, should decrease a friction coefficient value. Two manufactured types of composites: Al2O3 – GC foam and own produced glassy carbon foam were compared with material reinforced by spatial carbon structure obtained from commercial RVC (produced by Reynolds) foam. The results showed that the application of porous ceramic and ceramic – carbon reinforcement skeletons led to increasing of mechanical properties of composite. The conducted research using pin–on–disc method, with 2,5 MPa of load and 1,0 m/s of speed revealed that glassy carbon have significant influence on decreasing friction coefficient and wear rate. An analysis of material external layer in areas after coupling with pin (wear track) indicated a fragmentation of glassy carbon foam. The wear products are not remove from friction surfaces, but these products create thin carbon film with lubricant properties. The conducted research showed both, a possibility to produce composites with skeleton structure of reinforcement and a possibility of correction of material tribological properties using glassy carbon.
44
Salehi, Akram, Ahmad Moloodi, Faezeh Barzegar e Jalal Mirabbasi. "The Effect of Sintering Condition on Microstructural and Mechanical Properties of Porous Nickel". Materials Science Forum 933 (ottobre 2018): 11–16. http://dx.doi.org/10.4028/www.scientific.net/msf.933.11.
Testo completoAbstract (sommario):
The relationship between temperature of sintering in neutral atmosphere and compression strength has been investigated for nickel foams produced by electrodeposition on an organic foam. The as-plated nickel foams are sintered at 600and 1000 in order to eliminate polyurethane and enhance ductility. The results show that the compression strength is significantly influenced by sintering temperature. The most ductile sample is gained by sintering at 600. In addition, samples sintered at this temperature have the higher energy absorbing capability. EDX analyses show that oxygen element raised from oxidation in high temperature presents in specimen sintered at 1000. Hollow struts are obvious in SEM image of treated foams. Keywords: Nickel foam, electrodeposition, EDX, Compression test
45
Xu, Huijin, Yan Wang e Xingchao Han. "Analytical considerations of thermal storage and interface evolution of a PCM with/without porous media". International Journal of Numerical Methods for Heat & Fluid Flow 30, n. 1 (19 giugno 2019): 373–400. http://dx.doi.org/10.1108/hff-02-2019-0094.
Testo completoAbstract (sommario):
Purpose Phase change energy storage is an important solution for overcoming human energy crisis. This study aims to present an evaluation for the thermal performances of a phase change material (PCM) and a PCM–metal foam composite. Effects of pore size, pore density, thermal conductivity of solid structure and mushy region on the thermal storage process are examined. Design/methodology/approach In this paper, temperature, flow field and solid–liquid interface of a PCM with or without porous media were theoretically assessed. The influences of basic parameters on the melting process were analyzed. A PCM thermal storage device with a metal foam composite is designed and a thermodynamic analysis for it is conducted. The optimal PCM temperature and the optimal HTF temperature in the metal foam-enhanced thermal storage device are derived. Findings The results show that the solid–liquid interface of pure PCM is a line area and that of the mixture PCM is a mushy area. The natural convection in the melting liquid is intensive for a PCM without porous medium. The porous medium weakens the natural convection and makes the temperature field, flow field and solid–liquid interface distribution more homogeneous. The metal foam can greatly improve the heat storage rate of a PCM. Originality/value Thermal storage rate of a PCM is compared with that of a PCM–metal foam composite. A thermal analysis is performed on the multi-layered parallel-plate thermal storage device with a PCM embedded in a highly conductive porous medium, and an optimal melting temperature is obtained with the exergy optimization. The heat transfer enhancement with metal foams proved to be necessary for the thermal storage application.
46
Ghosh, Pinaki, e Kishore K. Mohanty. "Novel Application of Cationic Surfactants for Foams With Wettability Alteration in Oil-Wet Low-Permeability Carbonate Rocks". SPE Journal 23, n. 06 (26 settembre 2018): 2218–31. http://dx.doi.org/10.2118/179598-pa.
Testo completoAbstract (sommario):
Summary Carbonate rocks are typically heterogeneous at many scales, leading to low waterflood recoveries. Polymers and gels cannot be injected into nonfractured low-permeability carbonates (k < 10 md) because pore throats are smaller than the polymers. Foams have the potential to improve both oil-displacement efficiency and sweep efficiency in such carbonate rocks. However, foams have to overcome two adverse conditions in carbonates: oil-wettability and low permeability. This study evaluates several cationic-foam formulations that combine wettability alteration and foaming in low-permeability oil-wet carbonate cores. Contact-angle experiments were performed on initially oil-wet media to evaluate the wettability-altering capabilities of the surfactant formulations. Static foam-stability tests were conducted to evaluate their foaming performance in bulk; foam-flow experiments (without crude oil) were performed in porous media to estimate the foam strength. Finally, oil-displacement experiments were performed with a crude oil after a secondary gasflood. Two different injection strategies were studied in this work: surfactant slug followed by gas injection and coinjection of surfactant with gas at a constant foam quality. Systematic study of oil-displacement experiments in porous media showed the importance of wettability alteration in increasing tertiary oil recovery for oil-wet media. Several blends of cationic, nonionic, and zwitterionic surfactants were used in the experiments. In-house-developed Gemini cationic surfactant GC 580 was able to alter the wettability from oil-wet to water-wet and also formed strong bulk foam. Static foam tests showed an increase in bulk foam stability with the addition of zwitterionic surfactants to GC 580. Oil-displacement experiments in oil-wet carbonate cores revealed that tertiary oil recovery with injection of a wettability-altering surfactant and foam can recover a significant amount of oil [approximately 25 to 52% original oil in place (OOIP)] over the secondary gasflood. The foam rheology in the presence of oil suggested propagation of only weak foam in oil-wet low-permeability carbonate cores.
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Nowacki, J., e A. Sajek. "Trends of Joining Composite AlSi-SiC Foams". Advances in Materials Science 19, n. 1 (1 marzo 2019): 70–82. http://dx.doi.org/10.2478/adms-2019-0006.
Testo completoAbstract (sommario):
AbstractThe paper consist of characterization of the essence of structure, properties and application of AlSi-SiC composite foams as well as limitations and possibilities of their joining. Porous structure with porosity up to 80% and exceptional properties of aluminium foams are the reason of their numerous application and interest of their joining. Consideration of methods of welding, soldering and gluing AlSi9-SiC10 composite foams, the joint structure, and properties. Recommendations for surface preparation of foam, and different joining procedures aimed at control the porosity of the foam and glued surface roughness were established. Result of EDS and XRD investigations of the AlSi9-SiC10 composite foams joint were considered.
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Mohd Razali, Razmi Noh, Bulan Abdullah, Muhammad Hussain Ismail e Norhamidi Muhamad. "Characteristic of Modified Geometrical Open-Cell Aluminum Foam by Casting Replication Process". Materials Science Forum 846 (marzo 2016): 37–41. http://dx.doi.org/10.4028/www.scientific.net/msf.846.37.
Testo completoAbstract (sommario):
In this work, aluminium foams with modified geometry were successfully fabricated with a combination of dense and porous structure The main objective of this study were to determine the initial physical properties of aluminium foam with modified geometry in terms of density, porosity and morphology. Three different NaCl space holder sizes ranging from 1 mm to 3 mm were sieved and used to replicate the final pore size of aluminium foam. The samples were successfully produced through casting replication process. After densification, samples underwent water leaching in ultrasonic bath to remove completely the space holder. Results showed that porosity of the aluminium foam increased from 50 – 62% when the size of space holder was increased from 1 mm to 3 mm. The morphology showed clearly an integrated modified geometry between dense and inter-connected porous structure which is beneficial for applications that require combination properties of structural, thermal and mechanical properties.
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Colson, Jérôme, Hassan Amer, Falk Liebner e Wolfgang Gindl-Altmutter. "Oil-absorbing porous cellulosic material from sized wood pulp fines". Holzforschung 73, n. 1 (19 dicembre 2018): 83–92. http://dx.doi.org/10.1515/hf-2018-0093.
Testo completoAbstract (sommario):
Abstract Fine fibres (fines) occur at various stages of the papermaking process. The high specific surface of fines may be of special interest in applications beyond papermaking. In the present study, foamy water suspensions of fines were freeze-dried, and in this way their porous structure was maintained. The density and porosity of these foams could be governed by varying the water content of the suspensions. The obtained matrices were highly hydrophobic because of the sizing applied during the papermaking process. Consequently, a high oil sorption capacity of the fines was observed. Up to a porosity of 98%, more than 80% of the overall volume of the foam-like material could be soaked with liquid. At higher porosities, the absorbed volume decreased. Mechanical reinforcement of the foams with poly(methyl methacrylate) (PMMA) as accomplished by dip-coating had no negative impact on the sorption behaviour. However, the performance of reinforced samples suffered from strong shrinkage upon drying, especially for high porosity matrices.
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Wang, Jinping, Naveed Mushtaq, M. A. K. Yousaf Shah, Jiaen Wu, Henghui Li, Yuzheng Lu e Peng Wang. "Oxygen Reduction Response of La and Ce Co-Doped SrCoO3-δ Perovskite Oxide Grown on Porous Ni-Foam Substrate". Crystals 12, n. 11 (16 novembre 2022): 1650. http://dx.doi.org/10.3390/cryst12111650.
Testo completoAbstract (sommario):
Lately, ceramic fuel cells (CFCs) have held exceptional promise for joint small- and large-scale applications. However, the low-oxygen reduction response of cathode materials has hindered the low operating temperature of CFCs. Herein, we have developed a semiconductor based on La and Ce co-doped SrCoO3 and embedded them in porous Ni-foam to study their electrochemical properties. The porous Ni-foam-pasted La0.2Sr0.8Co0.8Ce0.2O3-δ cathode displays small-area-specific resistance and excellent ORR (oxygen reduction reaction) activity at low operating temperatures (LT) of 450–500 °C. The proposed device has delivered an impressive fuel cell performance of 440 mW-cm−2, using La0.2Sr0.8Co0.8Ce0.2O3−δ embedded on porous Ni-foam substrate cathode operation at 550 °C with H2 fuel and atmospheric air. It even can function well at a lower temperature of 450 °C. Moreover, La0.2Sr0.8Co0.8Ce0.2O3−δ embedded on porous Ni-foam shows very good activation energy compared to individual SrCoO3 and La0.1Sr0.9Co0.9Ce0.1O3−δ embedded on porous Ni-foam, which help to promote ORR activity. Different characterization has been deployed, likewise: X-ray diffraction, photoelectron-spectroscopy, and electrochemical impedance spectroscopy for a better understanding of improved ORR electrocatalytic activity of prepared La0.2Sr0.8Co0.8Ce0.2O3−δ embedded on porous Ni-foam substrate. These results can further help to develop functional cobalt-free electrocatalysts for LT-SOFCs.