Procedia Materials Science最新文献

The effect of different variables (reactive precursors, additives, stoichiometric ratio) on the final morphology of nano-ZnO obtained by a microwave-assisted technique has been investigated. The characterization of the samples was carried out by scanning electron microscopy in transmission mode (FE-SEM), infrared spectroscopy (FTIR) and x-ray diffraction (XRD). The results showed that all the above-mentioned variables influenced to some extent, the shape and/or size of the synthesized nanoparticles. In particular, the addition of an anionic surfactant (sodium di-2-ethylhexyl sulfosuccinate, AOT) to the reaction mixture allowed the synthesis of complex tridimensional particles with uniform size distributions and morphology.

In this paper, we report the synthesis and characterization of composites of polyaniline and aluminum doped tin oxide (Al-SnO₂/PANI) nanofibers for hydrogen gas sensing application. Al-SnO₂/PANI composite nanofibers have been fabricated via electrospinning technique and subsequent calcination procedure. The as-prepared Al-SnO₂/PANI composite nanofibers were investigated for structural characterizations by means of SEM, FTIR, UV-VIS and XRD. SEM revealed the nanofibers with the diameter around 200-300 nm formed a non-woven material with highly porous and agglomerated structure. FTIR and UV-VIS spectra revealed the possible incorporation of Al-SnO₂ in PANI and confirmed the uniform attachment of PANI on the surface of Al-SnO₂ nanostructures. XRD showed peak broadening and the peak positions shift from standard values, indicating presence of aluminum doped tin oxide in nanoparticles form in the polyaniline (PANI) matrix. On exposure to hydrogen gas (1000 ppm), it was found that the nanofibers of Al-SnO₂/PANI composite showed high sensitivity at 48 ^oC with relatively faster response/recovery as compared to pure SnO₂ and Al doped SnO₂ nanofibers.

The effect of addition of nano clay and water absorption on jute fibreshas been studied. Although glass and other synthetic fibre-reinforced plastics possess high specific strength, their fields of application are very limited because of the inherent higher cost of production. To overcome this limitation, an investigation has been carried out to make use of jute, a natural fibre which is abundantly available at lower cost. In the present work, a new composite is developed in which jutefibresare reinforced with polyester resin and with the addition of nano clay.Themechanical properties of the new composite are evaluated. The wide variety of bio composite processing techniques as well as the factors such as moisture content, fibre type and content, and their influence on composites properties are discussed. The addition of nano clay to the jutefibre reinforced composites exhibited significant improvement in the mechanical propertiesat lower cost and therefore can be used as a substitute to glass and synthetic fibres.

UAl₃ - USi₃ equilibrium phase diagram has already been analyzed by the present authors in a previous work based in a set of ab initio calculated energies for volume relaxed ordered structures. We evaluate in this work the formation energy of the disordered phase U(Al,Si)₃ through a cluster expansion method from ab initio calculated total energies for full relaxed ordered structures. Total energies were calculated through a DFT based FP LAPW method in the GGA approximation, including scalar relativistic corrections and implemented in the WIEN2K code. Cluster expansion and Monte Carlo simulation for finite temperatures were performed with the aid of the program package ATAT. Ionic relaxation does not introduce variations neither in the transition temperatures nor in the general morphology of the equilibrium phase diagram. However, it allows the stabilization of a wide zone of ordering of the solid solution around the U₂Al₃Si₃ composition, and an ordering at low temperatures at U₂AlSi₅ composition.

The use of polymer fibre reinforced Composite materials is finding applications day by day in engineering fields such as aero-space, automotive, aircrafts constructions, etc. Glass fibre polymer composites are reinforced with granulated blast furnace slag (GBFS) ball milled to size of 5 nm in different weight fractions, i.e. (0%, 5%, 10% and 15%) and fabricated by using hand lay-up technique. These fabricated slabs are cut into required dimensions and the tests for mechanical properties like Tension test, Compression test, Flexural test Impact test and Hardness test were performed. Tension test, compression test and Flexural test were performed on Computerized Universal Testing Machine (UTM), Impact test was performed for Izod and Charpy specimens and Hardness test was performed on Brinell's Hardness Testing Machine. From the experimental results obtained, it was noticed that the mechanical properties were enhanced when the blast furnace slag percent was increased and also among these percentages of blast furnace slag, the specimen having 15% was possessing highest properties.

In the present work longitudinal residual stresses obtained by different methods, numerical and experimental, in Friction Stir Welding (FSW) process for AA7075 were analyzed. The experimental method employed for residual stresses measurements was sectioning, whereas the numerical is a finite element (FEM) thermomechanical coupled model which does not consider the stir in the material. The effect of travel speed during FSW was also analyzed, measuring with strain gages positioned in several points at different distances from weld centerline. From the obtained residual strains, the stress values, stress variation against weld centerline distance and null stress point were calculated. Numerical and experimental stress values agree in order of magnitude, being greater in numerical method inside stir zone's edge and even outside, and smaller at some point towards the end of plate. Stress variation against weld centerline distance and null stress position vary in different ways for each method. This phenomenon agrees with another works, and it could be related with no consideration of the stir process in the numerical method. Thus, it has been developed a simplified finite element model which averages in magnitude experimental residual stress in FSW.

In this paper an attempt has been made to study some of the elements of mathematical modeling in solid tumor growth. We present simple deterministic mathematical models used to describe tumor growth. Radiation therapy can be made very effective through the use of nanoscale particles such as gold nanoparticles, carbon nanotubes and magnetic nanoparticles. Development of a model using all the necessary biological assumption has been illustrated through an example. A large number of drug delivery systems have been developed over the years to overcome the challenges in cancer treatment and hence improve the right balance between effectiveness and toxicity. Finally we present various aspects of our methods and their results .The results demonstrate that the use of nanoscale particles in radiation treatment planning holds a lot of potential to improve the efficiency of the treatment.

The antimicrobial activity of silver nanoparticles makes this chemical element attractive for their incorporation in different materials. Additionally, heteropolyacids (HPAs) have advantages as catalysts which make them environmentally very interesting. The objective of this work is to incorporate in a silica matrix obtained by sol-gel an HPA together with Ag, for their use as fillers in paints or adhesives. Six samples were synthesized, using tetraethoxysilane, methyltrimethoxysilane, acetic acid, molybdophosphoric acid and silver acetate. The silicas were characterized by potentiometric titration, XRD, SEM, TEM, S_BET and FT-IR. When HPA is used instead of acetic acid, a variation on the final acidity is produced. The specific surface area decreases when HPA is incorporated into the silica synthesized using tetraethoxysilane as precursor, noticing a slight increase when Ag is added because a different distribution of HPA in the matrix. By SEM, it was observed that the particle size is bigger when the silicas are synthesized with TEOS-HPA, but it still shows the characteristic morphology of bulk silica. Additionally, preliminary test to evaluate the antimicrobial properties of the solids were carried out with fungi as Chaetomium globosum and Alternaria alternate, isolated from contaminated paints, and the first results are encouraging to continue with the development of these materials.