Recent innovations in geopolymer technology have led to the development of various different types of geopolymeric products, including highly porous geopolymer-based foams, which are formed by the ...addition of foaming agents to a geopolymer fly-ash based matrix. These agents decompose, or react with the liquid matrix or oxygen in the matrix, resulting in the release of gases which form pores prior to the hardening of the gel. The hardened structure has good mechanical and thermal properties, and can therefore be used for applications in acoustic panels and in lightweight pre-fabricated components for thermal insulation purposes.
This study presents the results of the pore-forming process in the case when two different foaming agents, i.e. aluminium powder amounting to 0.07, 0.13 and 0.20 mass. % and H2O2 amounting to 0.5, 1.0, 1.5 and 2.0 mass. %, were added to a fly-ash geopolymer matrix. The physical, mechanical, and microstructural properties of the thus obtained foams, and the effects of the type and amount of the added foaming agent, are presented and discussed. Highly porous structures were obtained in the case of both of the investigated foaming agents, with overall porosities up to 59% when aluminium powder was added, and of up 48% when H2O2 was added. In the latter case, when 2% of the H2O2 foaming agent was added, finer pores (with diameters up to 500μm) occurred in the structure, whereas somewhat larger pores (some had diameters greater than 1mm) occurred when the same amount of aluminium powder was added. The mechanical properties of the investigated foams depended on their porosity. In the case of highly porous structures a compressive strength of 3.3MPa was nevertheless achieved for the samples containing 0.2% of aluminium powder, and 3.7MPa for those containing 2.0% of H2O2.
•Preparation of geopolymer foams based on fly ash with the addition of Al powder or H2O2 as foaming agents•Determination of density, porosity and mechanical properties of such foams•Characterization of foaming process by means of X-ray micro-tomography (μcT)
This research experimented with different aluminum can casting compositions from recycled materials. The objective was to analyze the casting yield and the resulting chemical compositions of the ...process. In the first process, 20 kg of aluminum cans was melted, resulting in a 10.2 kg ingot, which presented a 51% yield. In the second process, 10 kg of 6063 T6 aluminum was used and 10.2 kg of the first casting was added. This mixture produced an ingot of 50% recycled aluminum and 50% 6063 aluminum that weighed 18.23 kg. Similarly, a second ingot was produced, but with the addition of 4 wt% of rice husk ash and 2 wt% of magnesium. From each ingot, the samples were removed for chemical analyses, which consisted of tests of the samples that had the incorporation of rice husk ash in the molten aluminum. These analyses included scanning by electron microscopy, density analysis, Brinell hardness, and Charpy impact force tests. The results of the second ingot analysis showed superior characteristics in Si and Mg levels due to the addition of rice husk ash and magnesium. Also, the second ingot presented increased hardness as well as a reduction fragility and density.
Aluminium (Al) is the most abundant metal in the earth’s crust. Al exposure can cause a variety of adverse physiological effects in humans and animals. Our aim was to demonstrate that specific ...probiotic bacteria can play a special physiologically functional role in protection against Al toxicity in mice. Thirty strains of lactic acid bacteria (LAB) were tested for their aluminium-binding ability, aluminium tolerance, their antioxidative capacity, and their ability to survive the exposure to artificial gastrointestinal (GI) juices.
Lactobacillus plantarum
CCFM639 was selected for animal experiments because of its excellent performance in vitro. Forty mice were divided into four groups: control, Al only, Al plus CCFM639, and Al plus deferiprone (DFP). CCFM639 was administered at 10
9
CFU once daily for 10 days, followed by a single oral dose of aluminium chloride hexahydrate at 5.14 mg aluminium (LD
50
) for each mouse. The results showed that CCFM639 treatment led to a significant reduction in the mortality rates with corresponding decrease in intestinal aluminium absorption and in accumulation of aluminium in the tissues and amelioration of hepatic histopathological damage. This probiotic treatment also resulted in alleviation of hepatic, renal, and cerebral oxidative stress. The treatment of
L. plantarum
CCFM639 has potential as a therapeutic dietary strategy against acute aluminium toxicity.
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•Grafting copolymerization occurred at the amino group of MBF was confirmed.•PSA and MBF-g-P(AM-DAC) played different roles in treatment of dyeing wastewater.•MBF-g-P(AM-DAC) improved ...settlement efficiency for bridging and adsorption.•Flocs possessed surface area of 24.8201 m2/g and adsorption capacity of 140 mg/g.
Congo red (CR) is a typical and widely used azo dye in industries. It possesses the serious threat to ecosystem and public for its indiscriminate discharge. Microbial flocculant (MBF) with various functional groups is a potential flocculant applied in dyeing wastewater treatment, and it has the advantages of high treatment efficiency, biodegradability and non-toxicity. In this study, the functional groups, amino group, ammonium group and acyloxy group, were grafted onto MBF to further improve its thermal stability, solubility and performance. Grafting copolymerization occurred at the amino group of MBF was confirmed by XPS. Polyaluminum silicate (PSA) and self-prepared functional microbial flocculant, MBF-g-P(AM-DAC), played different roles in CR wastewater treatment. PSA contributed to charge neutralization, but its yielded flocs were small. On the contrary, MBF-g-P(AM-DAC) possessed weak charge neutralization but big flocs. Its settlement efficiency has significantly improved. The unsaturated active sites on MBF-g-P(AM-DAC) and its flocs contributed to the adsorption of CR in terms of high surface area and adsorption capacity of the flocs. Physical adsorption and chemical adsorption were both discovered in the treatment.
Laser Shock Peening is a fatigue enhancement treatment using laser energy to induce compressive Residual Stresses (RS) in the outer layers of metallic components. This work describes the variations ...of introduced RS‐field with peen size and coverage for thin metal samples treated with under‐water‐LSP. The specimens under investigation were of aluminium alloy AA2024‐T351, AA2139‐T3, AA7050‐T76 and AA7075‐T6, with thickness 1.9 mm. The RS were measured by using Hole Drilling with Electronic Speckle Pattern Interferometry and X‐ray Diffraction. Of particular interest are the effects of the above mentioned parameters on the zero‐depth value, which gives indication of the amount of RS through the thickness, and on the value of the surface compressive stresses, which indicates the magnitude of induced stresses. A 2D‐axisymmetrical Finite Element model was created for a preliminary estimation of the stress field trend. From experimental results, correlated with numerical and analytical analysis, the following conclusions can be drawn: increasing the spot size the zero‐depth value increases with no significant change of the maximum compressive stress; the increase of coverage leads to significant increase of the compressive stress; thin samples of Al‐alloy with low Hugoniot Elastic Limit (HEL) reveal deeper compression field than alloy with higher HEL value.
The demand for aluminum alloys is increasing because of their lightness, high specific strength and other attractive properties, which can exploited in improved products for a greener environment. ...This book gives a correlation between the processing, microstructure and properties of several aluminium alloys. Some of them are well established and used in an enormous number of applications, while others are still under development. The processing spans from casting, rapid solidification, additive manufacturing, forming, heat-treatment and welding, which can produce interesting microstructures and a useful combination of properties.
In this work, aluminum matrix composites reinforced with diamond particles (diamond/aluminum composites) were fabricated by squeeze casting method. The material exhibited a thermal conductivity as ...high as 613W/(m·K). The obtained composites were investigated by scanning electron microscope and transmission electron microscope in terms of the {100} and {111} facets of diamond particles. The diamond particles were observed to be homogeneously distributed in the aluminum matrix. The diamond{111}/Al interface was found to be devoid of reaction products. While at the diamond{100}/Al interface, large-sized aluminum carbides (Al4C3) with twin-crystal structure were identified. The interfacial characteristics were believed to be responsible for the excellent thermal conductivity of the material.
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•Squeeze casting method was introduced to fabricate diamond/Al composite.•Sound interfacial bonding with excellent thermal conductivity was produced.•Diamond{111}/ aluminum interface was firstly characterized by TEM/HRTEM.•Physical combination was the controlling bonding for diamond{111}/aluminum.•The growth mechanism of Al4C3 was analyzed by crystallography theory.
The second-order Møller-Plesset perturbation theory calculations with the aug-cc-pVTZ basis set were performed on complexes of triel species: BCl
, BH
, AlCl
, and AlH
acting as Lewis acids through ...the B or Al centre with Lewis base units: NCH, N
, NH
, and Cl
anion. These complexes are linked by triel bonds: B/Al⋅⋅⋅N or B/Al⋅⋅⋅Cl. The Quantum Theory of ´Atoms in Molecules´ approach, Natural Bond Orbital method, and the decomposition of energy of interaction were applied to characterise the latter links. The majority of complexes are connected through strong interactions possessing features of covalent bonds and characterised by short intermolecular distances, often below 2 Å. The BCl
⋅⋅⋅N
complex is linked by a weak interaction corresponding to the B⋅⋅⋅N distance of ~3 Å. For the BCl
⋅⋅⋅NCH complex, two configurations corresponding to local energetic minima are observed, one characterised by a short B⋅⋅⋅N distance and a strong interaction and another one characterised by a longer B⋅⋅⋅N distance and a weak triel bond. The tetrahedral triel structure is observed for complexes linked by strong triel bonds, while, for complexes connected by weak interactions, the structure is close to the trigonal pyramid, particularly observed for the BCl
⋅⋅⋅N
complex.
Research shows that monolithic Al alloy has very attractive properties required in the production of aerospace, automotive, electrical and electronic, sports and recreational components/equipment. ...However, its low strength and low wear resistance have challenged its applications in some other critical industrial utilities. Nonetheless, the invention of metal composites has removed such barriers. The addition of one or more reinforcements to Al has helped in the creation of aluminium matrix composites (AMCs), which has not only increased the global utilization of Al alloy, but has been a major source of global revenue and job. This review was, therefore, aimed at studying recent works on AMCs with the aim of ascertaining the recent innovations in the development of advanced Al composites, which can replace steel components in most industrial applications at a cheaper rate. It was observed from the study that AMCs can be developed via solid and liquid fabrication techniques. Powder metallurgy was reported as the most effective method of producing hybrid Al nanocomposites, with spark plasma sintering as the best technique. In the liquid process, stir casting was reported as the most cost effective, but was challenged by agglomeration. It was recommended that agglomeration be ameliorated by cryogenic ball milling and an in situ fabrication technique. It was also recommended that more cost effective agro-waste nanoparticles should be developed to replace more costly conventional reinforcements. In summary, it was recommended that more research on the exploration of Al alloy at a cheaper rate should be carried out.
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