M. Taherishargh

Fatigue properties of expanded perlite/aluminum syntactic foams:

The main purpose of this paper is to present the basic fatigue properties of metal matrix syntactic foams. The investigated syntactic foams consisting of expanded perlite and A356 aluminum matrix were produced using an inert gas pressure infiltration technique. The obtained foams were subjected to cyclic compressive loading in order to investigate their fatigue properties. The standard procedure for cyclic fatigue testing was slightly modified to account for the variation of porosity and strength which is typical for metallic foam samples. This approach allows the direct comparison of the fatigue test results between all investigated samples. Depending on the applied load level, two different failure mechanisms were identified that resulted in characteristic deformation – loading cycle curves. The failure mechanisms were further investigated on the microstructural scale: traces of fatigue beachmarks and extensive plastic deformation were found. Furthermore, Wöhler-like deformation – lifetime diagrams were created in order to predict the expected lifetime of the properties of metal matrix syntactic foams .

Controlled Shrinkage of Expanded Glass Particles in Metal Syntactic Foams

Metal matrix syntactic foams have been fabricated via counter-gravity infiltration of a packed bed of recycled expanded glass particles (EG) with A356 aluminum alloy. Particle shrinkage was studied and has been utilized to increase the particles’ strength and tailor the mechanical properties of the expanded glass/metal syntactic foam (EG-MSF). The crushing strength of particles could be doubled by shrinking them for 20 min at 700 °C. Owing to the low density of EG (0.20–0.26 g/cm3), the resulting foam exhibits a low density (1.03–1.19 g/cm3) that increases slightly due to particle shrinkage. Chemical and physical analyses of EG particles and the resulting foams were conducted. Furthermore, metal syntactic foam samples were tested in uni-axial compression tests. The stress-strain curves obtained exhibit three distinct regions: elastic deformation followed by a stress plateau and densification commencing at 70–80% macroscopic strain. Particle shrinkage increased the mechanical strength of the foam samples and their average plateau stress increased from 15.5 MPa to 26.7 MPa.

Long-term immersion exposure of perlite–aluminium syntactic foam in seawater:

Perlite–metal syntactic foam is a novel lightweight material with good specific strength and excellent energy absorption capabilities. To analyse its suitability in marine applications, perlite–metal syntactic foam has been immersed for 2 years in natural flowing seawater. The change of mass and mechanical properties has been studied as a function of exposure time. Results indicate a slow degradation of mechanical properties that can be attributed to a change of the macroscopic deformation mechanism. Interestingly, no evidence of significant corrosion was observed. Instead, the change in mechanical properties is triggered by the sedimentation of oxides and sulphates within the expanded perlite particles. Implications towards the long-term viability of such perlite–metal syntactic foam in marine applications are discussed.

Large-scale drop test on perlite–metal syntactic foam:

Perlite–metal syntactic foam is a low-cost cellular metal intended for use in automotive impact protection. To test the viability of the material a 2.5 ton drop test was conducted. Impact mass and energy were selected to replicate the conditions of a frontal impact between a large passenger vehicle and a crash cushion. A hollow syntactic foam cylinder was manufactured to decelerate the drop weight in a controlled manner. Accelerometers and high-speed imaging were utilized to evaluate the performance of the energy absorbing element.

Perlite metal syntactic foam (PMSF) in impact engineering

M solvothermal process was used to synthesize anatase TiO2 nanocrystallines for the application of dyesensitized solar cells (DSSCs). The morphologies and sizes of TiO2 could be simply controlled by using different kinds of alcohols where no additives were needed. By using isopropanol (IPA) as solvent, TiO2 in size of 20-30 nm with dominant {001}/{010} facets was obtained; whereas ultrafine anatase TiO2 of about 5 nm with dominant {101}-facet was obtained using octanol (OCT). To investigate the influences of TiO2 on the photovoltaic performances of DSSCs, three different pastes were fabricated using IPA, OCT and mixed IPA/OCT as photoanodes. The results revealed that the requirements of TiO2 photoanodes used at one sun and room light conditions were quite different. OCT showed the highest power conversion efficiency (PCE) up to 9.58% under one sun irradiation because of its high specific surface area that provided high dye-loading capacity. However, the great amount of grain boundaries appeared in OCT became disadvantageous at room light condition. On the other hand, IPA/OCT combined the features of IPA and OCT that was optimal for room light harvesting and its PCE reached 12.46% under 200 lux T5 lamp irradiation. The photovoltaic properties of three different photoanodes in correlation with their band structures, electronic transport behaviors and light harvesting efficiency in different lighting conditions will be carefully discussed in this presentation.G the increasing interest for the biomaterials in medical and engineering field, the objective of this talk is the theoretical and experimental analysis of the biomaterials in order to define experimental procedures and mathematical models suitable for their mechanical characterization. The biomaterials exhibit a rheological behavior intermediate between that of purely elastic materials and that of the purely viscous materials and therefore are called viscoelastic ones. In the past the “classical” models as Maxwell and Kelvin-Voigt have been used to capture viscoelastic phenomena. However, these models are not consistent to model the viscoelastic behavior of real materials, since the Maxwell type can capture the relaxation tests only and the Kelvin-Voigt the creep tests. A more realistic description of creep and/or relaxation is given by a power law function with real order exponent. As soon as we assume a power law function for creep, the constitutive law relating deformation and stress is ruled by a Riemann-Liouville fractional integral with order equal to that of the power law. In this regard, recent studies have been stressed that the most suitable model for capturing the viscoelastic behavior is the spring-pot, characterized by a fractional constitutive law. Based on the aforementioned considerations, it is apparent that the need of theoretical as well as experimental development and exploration of materials with novel physical characteristics. For instance, if the giant grass Arundo donax (AD) has to be characterized; then, attention is devoted on searching a proper model for characterizing the behavior of giant reeds. To aim at this, firstly, meticulous experimental tests have been performed in the Laboratory of structural materials of University of Palermo. Further a novel aspect of using an advanced Euler-Bernoulli model to fit experimental data of bending tests will be introduced.M devices represent an emerging technology with a great potential in analytical life sciences. In particular lab-on-a-chip concerning genomic applications has attracted great interest; in such systems there is often the need to provide an efficient DNA amplification by PCR (polymerase chain reaction). Nowadays, polymers are the materials of choice for the fabrication of micro devices for genomic applications. For prototyping and small-scale production, soft lithographyA family of multiple-step techniques based on molding the thermally curable elastomer polydimethylsiloxane (PDMS) is the current gold standard. However, the commercial and common thermally curable PDMS shows some drawbacks that limit its applicability in biotechnology, such as the difficulty in controlling and modifying the surface chemistry and in tuning the physical and mechanical properties of the material. An appealing alternative to thermally curable PDMS prototyping is the use of specially designed UV curable polymers, as photopolymerization is a very fast reaction that leads to the synthesis of highly cross-linked networks in few seconds at room temperature. Moreover, this technique can be applied to a wide variety of photocurable polymers, allowing to select and tune the desired physico-chemical properties of the final device. In the present work, we introduce the use of a class of photocurable siloxane polymers for the fabrication of microfluidic devices for biomedical applications (i.e., PCR). New multifunctional acrylic oligomers are synthesized (Figure 1a) and then photo cross linked. Moreover, copolymerization is used as strategy to optimize the photopolymer properties. The polymers and copolymers synthesized are suitable for bio microfluidics: they are PCR compatible (Figure 1b), highly resistant to temperature and various solvents, transparent, dimensionally stable and essentially non-permeable to water vapor. Therefore, these materials are used to fabricate microfluidic devices (Figure 1c), in which PCR is successfully conducted as proof of principle.

Effect of Processing Parameters on Thermo-Mechanically Affected Zone of Friction Stir Processed AZ91 Magnesium Alloy

AZ91 Magnesium alloy was subjected to friction stir processing (FSP). The microstructural analyses of the friction stir processed (FSPed) specimens were carried out and the effects of pass number, rotational speed, and traverse speed upon thermo-mechanically affected zone (TMAZ) were investigated. The TMAZ is consisted of a region with highly elongated grains and a partially recrystalized zone. Decreasing the rotational speed and increasing the traverse speed increased the thickness of recrystallized zone; while, the thickness of the other zone decreased. On the other hand, it lessened the gradient of the grain size from the stir zone (SZ) to the base metal. Applying several FSP passes, lead to more homogeneous TMAZ structure with the finer grain size.Copyright