Strength Of Foams Research Articles

An Alternative Method for the Obtention of Ceramic Foams from Gold and Silver Tailings with High Pyrite Content

Mining extraction operations generate a large number of tailings that contain different mineral phases such as quartz (principally), complex silicates, metallic elements, etc. Tailings impose a serious concern as it is possible to have acid mine drainage potential, leaching, and percolation events of heavy metals into the environment under certain conditions. The objective of this work was to evaluate the technical feasibility of producing ceramic foams from gold and silver tailings with high sulfide gangue through a previous flotation process to eliminate impurities associated to this gangue, as it can produce SO2 in the foaming process, and to analyze the effect of the sintering time and the temperature on the characteristics of foams obtained with this type of waste. The results showed that the inverse flotation reduced the presence of impurities associated to sulfides. In addition, it was possible to observe that in the absence of a foaming agent, it was possible to obtain ceramic foams with an apparent density and a mechanical strength near to 1.0 g/cm3 and 0.5 MPa, respectively, when a higher sintering temperature and time were used. On the other hand, the presence of the foaming agent reduced the apparent density to 0.5 g/cm3 without decreasing to a great extent the mechanical strength of ceramic foams at lower sintering temperatures.

Hybrid polymeric-metallic foams for bone tissue engineering scaffolds: mechanical properties and biofunctionality evaluations

Challenges exist in the applicability of thermoplastic foams as scaffolds for bone tissue engineering including mismatch of mechanical properties. Template assisted electrodeposition was carried out to fabricate hybrid polymeric-metallic foams. Compression test, cytotoxicity and biofunctionality evaluations was performed on polyurethane coated niobium foams to investigate the enhancement of desired properties. Results indicated that ultimate compressive strength of polyurethane foams improved due to the niobium coatings. Biocompatibility evaluations showed that the niobium coated foams were biocompatible. Bio-functionality evaluations showed that the coating of niobium on polyurethane decreases its ability to support osteoblastic cell attachment and proliferation.

Microstructure and compressive properties of solution heat-treated magnesium-Mg2Si in-situ composite foams after complex modification

In this study, open-cell Mg composite foams reinforced with in-situ Mg2Si were prepared. In order to refine the Mg2Si compound, the composite foams were co-modified with Y + Sb elements followed by solution heat treatment. The influences of complex modification and holding time of solution heat treatment on the microstructure and compressive properties of the composite foams were studied. The experimental results show that the morphology of Mg2Si is effectively changed by complex modification. The coarse dendritic primary Mg2Si (∼40 μm) is altered to the fine polygonal shape (∼10 μm); the coarse eutectic Mg2Si is transformed to a long rod or granular shape. Both compressive strength and energy absorption capacity of the composite foams are significantly increased. Additionally, with the increasing holding time of solution heat treatment, the eutectic Mg2Si undergoes obvious spheroidization, and the corner of the primary Mg2Si occurs passivation. Consequently, the compressive strength and energy absorption capacity are further improved.

Impact of oil and wettability on foam-assisted conformance control in a Middle Eastern carbonate reservoir

Gas injection has been evaluated and implemented in the large carbonate oil field located offshore Qatar as water alternating gas or WAG. It has been seen that WAG is economically viable and a robust enhanced oil recovery (EOR) method for homogenous formations. However, using WAG in heterogeneous parts of the field has not been attempted due to issues like early gas breakthrough and unfavourable sweep efficiency. Hence, it was decided to design a foam-assisted WAG system that can provide the required conformance control to mitigate those issues and expand the use of WAG. A complete laboratory programme was carried out to screen the best foaming surfactant formulation that resulted in the selection of environmentally friendly, Alkyl polyglucoside (APG) surfactant. Surfactant testing involved foamability in porous media under oil-wet and water-wet conditions in presence of residual oil to gas flood. The chosen surfactant showed good foam strength in both cases with effective mobility reduction factors (MRF) above 20. The impact of mobile oil was also observed by co-injecting oil during linear core flood experiments, which clearly showed that good foam strength could be achieved in a lower flow fraction of mobile oil with foam. Additionally, boosting of foam strength using amphoteric Lauryl Betaine (LB) surfactant was also performed. The formulation with APG/LB (70%/30%) gives foam boosting of 2.5 times compared to foam strength using APG alone. Additionally, it was shown that altering wettability using a nonionic Tergitol surfactant (TGT-1) as pre-flush and then injecting APG-5 surfactant and methane resulted in foam strength, which is 1.5 times higher than observed in oil-wet conditions.

Effects of hollow glass microspheres on the polybenzoxazine thermosets: Mechanical, thermal, heat insulation, and morphological properties

AbstractThe growing need for high thermal and mechanical resistant lightweight syntactic foams demands the designing of new materials. Herein, we report the successful fabrication of lightweight and high thermal resistance syntactic foams with excellent thermal and good mechanical properties. For this end, 10–50 wt% hollow glass microsphere (HGMS) containing polybenzoxazine based syntactic foams were prepared by using bisphenol‐A‐aniline (BA‐a) and phenol‐diaminodiphenylmethane (P‐ddm) benzoxazine via curing at 10 MPa compression molding. The curing behavior, tensile, flexural, compressive, and impact strength, thermal properties, and fracture morphology of the syntactic foams were studied by DSC, universal material testing machine, and drop hammer impact testing machine, TGA, and SEM, respectively. The curing temperatures of BA‐a and P‐ddm benzoxazine resins were slightly increased after blending the HGMS. The highest decline (59%) in the density and highest void contains (13.17%) was recorded for the poly(P‐ddm/HGMS50) sample. The excellent specific mechanical properties of the syntactic foams were observed on the 30 wt% HGMS loading. The thermal conductivity of the foams was gradually decreased and the lowest values of 0.106 and 0.0985 W/m.K were observed for poly(BA‐a/HMGS50) and poly(P‐ddm/HGMS50) sample, respectively. Furthermore, a gradual improvement in the thermal properties was observed as the loading of HGMS increased.

Splitting and curling collapse of metal foam core square sandwich metal tubes: Experimental and theoretical investigations

Axial splitting and curling collapse of square sandwich metal tubes with metal foam core is investigated analytically and experimentally. The square sandwich metal tube split axially and curl outward along prefabricated cracks. Axial compressive tests of square sandwich metal tubes with prefabricated cracks are conducted and deformation modes are observed. An analytical model for axial splitting and curling behavior of square sandwich metal tube considering plastic bending, crack tearing, curling, foam compression, friction is proposed. It is demonstrated the analytical predictions are in good agreement with experimental results. Influences of foam thickness, tube thickness, die angle, prefabricated crack length, and foam strength are of vital importance to axial splitting and curling of square sandwich metal tube.

Effects of high‐temperature exposure on properties of lightweight geopolymer foams incorporating diatomite powders

AbstractA kind of metakaolin‐based geopolymer foams incorporating diatomite powders (GKGP) with open cellular was presented by addition of diatomite powder via hydrogen peroxide method. Impacts of high‐temperature exposure on the microstructure, pore structure, and mechanical properties of the GKGP samples were investigated. The GKGP foams achieved a typical amorphous phase structure at room temperature. Open porosity of the samples reached approximately 74%. After high‐temperature exposure treatment, the KGP matrix is basically transformed into leucite crystal phase. The compression strength of the leucite foams was also enhanced with increasing temperature to 1200℃ (9.28 MPa). The lightweight foamed GKGP samples with high open porosity might have great potential for membranes and industries, etc.

Structural properties of cellulose nanofibril foam depending on wet foaming conditions in Pickering stabilization

Porous cellulose nanofibril (CNF) foam was prepared by stabilizing bubbles with CNF and a surfactant and then drying the stabilized wet foam in a convection oven. The consistency of carboxymethylated CNF (CMCNF) and the addition amount of the surfactant were controlled and the effects of these factors on the CNF wet foam and dry foam properties were investigated. An adequate amount of the surfactant (0.02–0.04 wt%) with CMCNF consistency higher than 0.5 wt% yielded wet foams with excellent stability. When the wet foam was dried at 60 °C in an oven, dry CNF foam with over 97% porosity was generated. The stable wet foams resulted in dry CNF foam with a sphere-like pore structure and low levels of shrinkage during drying. In contrast, unstable wet foams generated dry foam with severe shrinkage and large cavities. The pore size and the porosity of the dried foam were determined by the shape of bubbles in the wet foam and the degree of shrinkage during drying, which, in turn, affected the mechanical strength. In addition, the compressive strength of the oven-dried foam was 83% higher than that of the freeze-dried foam. Therefore, the preparation of a stable wet porous CMCNF foam by controlling the CMCNF consistency and the amount of surfactant was essential for obtaining a porous CMCNF foam with a uniform pore structure and good mechanical strength by oven drying.Graphic abstract

Probing the Effect of Wettability on Transport Behavior of Foam for Enhanced Oil Recovery in a Carbonate Reservoir

Foam for enhanced oil recovery in carbonate reservoirs is generally challenging because the oil-wet formation is not favorable for generating and stabilizing the lamellae. With an alkyl-polyglucoside surfactant, a series of foam core flooding experiments both in the absence and in the presence of crude oil were performed on Estaillades limestone, a dual porosity and heterogeneous carbonate presenting reasonable similarities with the reservoir formation. The effects of wettability, surfactant concentration, and foam quality on foam strength were systematically investigated. It is found that the foam strength in the presence of oil is generally smaller than that in the absence of oil, and the foam strength in the oil-wet condition is typically lower than that in the water-wet condition. However, for the water-wet condition, the foam strength can be greatly improved by increasing the surfactant concentration, which is getting closer to that in the absence of crude oil at a sufficiently high surfactant concentration. The combined effect of a high remaining oil saturation and the disadvantageous wettability can further destabilize foam, thereby greatly reducing the foam strength at oil-wet conditions. As a result, the foam flooding under the water-wet condition outperforms that at the oil-wet condition. Furthermore, it is found that the foam behavior at a high gas fraction is more sensitive to the wettability of rock and the foam hysteresis effect.

Co-cured manufacturing of multi-cell composite box beam using vacuum assisted resin transfer molding

Co-curing holds great promise to minimize assembly weight, time, and cost for stiffened aerospace structures, which are conventionally fabricated separately and then integrated either through mechanical fastening or adhesive bonding—also known as secondary bonding. This study presented a low-cost co-curing process using VARTM to fabricate stiffened shells, particularly composite box beams. The experimental investigation was performed and the co-curing process was improved by scrutinizing the critical process parameters, such as foam strength and coating, and curing cycle. This work was also intended to present the demonstration of the proposed co-curing method and its comparison with the conventional secondary bonding technique for three-cell carbon fiber-reinforced polymer (CFRP) composite box beams. Fiber volume fraction measurements were carried out to the specimens extracted from the various section of the co-cured part, namely top skin, web, and bottom skin and as a result, around 60% of fiber volume fraction was measured, which was in good agreement with the results obtained from optical microscopy-based image analysis. Structural-level four-point bending test results showed that the weight normalized maximum and the ultimate load of the part increased by 44% and 45% with the use of the co-curing process, respectively. The improved mechanical properties indicated that stronger structural integration can be achieved by integrally curing structures. SEM micrographs revealed a favorable fiber-matrix interface, bolstering the superior integration of the co-cured part. These findings suggest that the low-cost co-curing process can be a potential candidate for the fabrication of stiffened aerospace structures, such as composite box beams.

A Graphical Interpretation Technique to Evaluate Strength and Stability of Foam in Porous Media Based on Mobile-Trapped Foam Ratio

A Graphical Interpretation Technique to Evaluate Strength and Stability of Foam in Porous Media Based on Mobile-Trapped Foam Ratio

Mechanical and Electromagnetic Shielding Properties of Carbon Foam

More importance is being attached to the harm caused by electromagnetic interference (EMI) problems. Plenty of research in this field has used carbon foam materials to solve EMI, and some excellent results are obtained, whereas the mechanical properties of carbon foam are poor, which limit applications in particular fields. The physical mechanism of electromagnetic shielding is unanswered and further study is needed. Herein, a kind of carbon foam material is obtained by the templating method; the effect of foam structure on the electromagnetic shielding properties of the carbon foam material is investigated through experiment and simulation. The electromagnetic shielding performance, mechanical properties, and thermal stability of carbon foam are also studied. The electromagnetic shielding performance of carbon foam material is 20 dB in the X‐band range with the thickness and density as 2 mm and , respectively. In addition, the compressive strength of the carbon foam is 0.55 MPa.

Improved tensile and impact responses of microcellular PP/γ-irradiated elastomer blends corroborating microstructure and crystallinity

The purpose of the present study was to compare the tensile and impact performances of foams of PP/γ-irradiated elastomer blends with that of the foams of PP/unirradiated elastomer blends. Furthermore, the morphological and crystallinity studies were considered to correlate the tensile and impact behavior of foams. Foaming of blends was carried out in a batch foaming set up with supercritical CO2. A continuous decrease in crystallinity was observed for both types of blends along with the relative change in the number of different crystal forms. Remarkable necking phenomenon and strain-induced crystallization were observed in foams. The tensile modulus of samples significantly increased up to 3 times than that of the neat samples at lower temperature foaming. The maximum modulus of foams was attained for the blends with 10% irradiated elastomer concentration. The impact strength of foam was also improved at the same condition, where the tensile modulus was highest.

Effect of Si Concentration of a Brazing Precursor on the Bonding Strength of Aluminum Foam Bonded via Foaming Bonding

Effect of Si Concentration of a Brazing Precursor on the Bonding Strength of Aluminum Foam Bonded via Foaming Bonding

Reticulated ceramic foams from alumina‐chromia solid solutions: A feasibility study

AbstractOpen cellular ceramic foams were manufactured from plain and chromia‐doped alumina, with a chromium concentration ranging between 1.25 mol% and 5.0 mol%. The (AlCr)2O3 starting powders were prepared by precipitation of a chromia precursor onto the surface of an alumina powder and subsequent calcination. Characterization of the starting powders as well as the foam samples made therefrom were carried out with respect to the chromium concentration in the alumina phase and the influence of the dopant on the cellular structure and sintering behavior of the doped material. While no positive effect on the compressive strength of the ceramic foams was found, the dopant influences the sintering behavior resulting in an increased shrinkage and in a reduction of total porosity.

Preparation and characterization of cordierite-based ceramic foams with permeable property from asbestos tailings and coal fly ash

The cordierite-based ceramic foams were successfully prepared by using asbestos tailings and coal fly ash (CFA) as main raw materials, without adding additional fluxing agent, and via the foaming agent method at a lower temperature. The influence of alumina content on the phase composition and structure of ceramic foams samples were investigated. At the same time, the influence of sintering temperature on phase evolution, physical and mechanical properties, microscopic morphology and water permeability were also studied. The results showed that the cordierite synthesized by the addition of 17.5% alumina had the better crystallinity. The addition of yellow sand could not only make up for the shortage of silicon sources in the raw materials, but also reduce the synthesis temperature of cordierite because it contained a certain amount of K+, Na+, Ca2+ and other fluxing components. Moreover, the bulk density, open porosity, water absorption, compressive strength and permeability coefficient of the cordierite-based ceramic foams prepared by the optimal formula S4 sintered at 1250 ℃ for 30 min were 0.77 g/cm3, 49.26%, 64.46%, 2.17 MPa and 0.71 mm/s, respectively. The product is expected to be used in the treatment of high-temperature exhaust gas and special waste water.

The Influence of Neem Oil and Its Glyceride on the Structure and Characterization of Castor Oil-Based Polyurethane Foam.

Neem (Azadirachta indica) oil is a non-edible oil that contains azadirachtin, which can be used as a biopesticide. This study synthesizes bio-based polyurethane (PU) foam from neem and castor (Ricinus communis L.) oil at normal temperature and pressure. Neem oil can be reacted to narrow-distribution polyol by transesterification of oil and glycerol. Neem oil glyceride (NOG) can be used as polyol for bio-based PU foams and can be blended with castor oil homogeneously to reduce the cost of production. The composition of polyol was castor oil and 0 to 20% molar ratios of NOG. Hexamethylene diisocyanate trimer (Desmodur N) was used as isocyanate. The molar ratios of NCO/OH were set as 1.0, 1.5 and 2.0. The average hydroxyl contents of castor oil, neem oil and NOG were 2.7 mmol/g, 0.1 mmol/g and 5.1 mmol/g, respectively. The reaction time of bio-based PU foam could be adjusted between 5 to 10 min, which is acceptable for manufacturing. The densities of PU foams were between 49.7 and 116.2 kg/m3 and decreased with increasing NCO/OH and NOG ratios and decreasing neem oil. The ranges of specific compressive strength of foams were from 0.0056 to 0.0795 kPa·m3/kg. Increasing the NOG and neem oil ratio significantly enhanced the specific compressive strength in the low NCO/OH ratio. The solvent resistance and thermogravimetric (TG) results showed that the foams have high water and thermal stability. NOG can help to increase solvent resistance. Adding neem oil reduces the solvent resistance. The results indicated that increasing NCO/OH and NOG ratios increases the cross-linking density and hard segment content of PU foams. This investigation demonstrated that castor oil-based PU foams are improved by adding NOG to the polyol mixture. PU foam has excellent properties. Neem oil can be used in manufacturing processes to produce high-performance foams via a green synthesis process.

Manufacturing of B4C particle reinforced A360 aluminium cellular composite materials by the integration of stir casting and space holder methods

Stir casting method has become prominent for fabrication of metal matrix composites in recent years. This method can be adjusted for casting around space holding particles to obtain cellular composite materials. In this study, a specific method which is a combination of stir casting and space holder techniques were used to produce open-celled A360 aluminium-B4C composite foams with regular sized and distributed pores. Weight ratios of reinforcement particles determined as 0.5, 1, 1.5 and 2%. The influences of particle reinforcement on the microstructure and the mechanical behaviour of composite foams were investigated. Microstructures were analysed with optical microscope (OM), scanning electron microscope (SEM). Compression and hardness tests were carried out to observe the effects of reinforcement on mechanical properties. Compression strength properties and hardness of composites increased with the ceramic reinforcement, however the plastic strength of the composite foams showed worsening trend after a certain reinforcement ratio (0.5 wt.%). Energy absorption properties of the composite foams showed parallel trends with compressive strength properties.

Нестандартные методы оценки качества интумесцентных покрытий

The main most frequently used structural materials are monolithic reinforced concrete, steel profiles and lightweight thin-walled building structures, which in case of fire at temperatures above 500 °C lose their mechanical properties, deform, and collapse. To protect the load-bearing structures from dangerous deformations for a certain time before the start of extinguishing a fire, various fire-retardant materials are used, among which thin-layer intumescent coatings occupy a special place. Serious problems with the quality of intumescent coatings are associated with the use by manufacturers of paint components (often counterfeit products of low quality) that do not correspond to those stated in the certificates. In these cases, the intumescent coating does not guarantee the formation of a high-quality protective layer of the coke foam in case of fire. Standard methods for assessing the quality of such coatings allow to assess appearance, thickness, and adhesion of the coating prior to coke foam formation. However, it is required to check directly on the object the additional non-standard parameters of the intumescent coatings: intumescence coefficient, appearance and strength of the coke foam. Ways are described related to the implementation of measuring the structural and mechanical properties of the coke foam: intumescence coefficient, penetration and shear-breakout strength. It is proposed to measure the strength characteristics of the coke foam by the penetrometry method on an original installation (analogue of a cone penetrometer). The proposed measurement method is simple, demonstrative and does not require expensive equipment. The dependence is revealed concerning the strength of the coke foam on its density, which is determined by the intumescence coefficient at all other things being equal. The higher the intumescence coefficient, the lower the density and strength of the coke foam. Therefore, high values of the intumescence coefficient do not guarantee the reliability of fire protection. It is recommended to set normatively limit values for the intumescence coefficient, which will differ for different compositions of the intumescent paints.

Metallurgical Characteristics, Compressive Strength, and Chemical Degradation Behavior of Aluminum-Cenosphere Composite Foam Developed by Spray Forming Route

In the present study, the microstructural characteristics, compressive strength, and corrosion behavior of aluminum-cenosphere composite foam (CF) developed by spray forming route (processed with 5 Psi (3.45 × 104 N/m2) and 10 Psi (6.90 × 104 N/m2) hydrogen pressure) has been undertaken. The microstructure of the spray-formed coupon consists of hollow cenosphere particles distributed uniformly in aluminum matrix. Compressive yield strength (YS) of the aluminum-cenosphere foam (CF) is different from commercially pure aluminum (cp-Al). It is found that the YS of the foam processed with 5 Psi is 83.62 MPa and for the foam processed at 10 Psi is 113.32 MPa as compared to 104.42 MPa for cp-Al. A detailed study of corrosion behavior through electrochemical measurements indicates that CF exhibits a reduced corrosion rate from 0.092 (for cp-Al) to 0.056 mm/year and 0.080 mm/year for the samples processed with 10 and 5 Psi, respectively. Through a detailed analysis of Nyquist and Bode plots derived from EIS measurements, it is concluded that mostly localized corrosion occurs in all the samples. The post-corrosion microstructural study confirms that interface of aluminum and cenosphere is the potential area for initiation of corrosion.