Revista de ciencias e ingeniería de materiales

Polystyrene-b-polybutadiene-b-poly (methyl methacrylate) block copolymer (SBM) was incorporated into epoxy resin to access the nanostructures in epoxy thermosets, knowing the different miscibility of polymeric blocks on epoxy matrix during the curing treatment. The morphology of modified SBM/epoxy resins was examined by Transmission and Field Emission Gun Scanning Electron Microscopy (TEM and FEG-SEM), reveling a nanostructured epoxy matrix with a dispersed micro-scale phase. The modified resins presented enhanced flexural properties, which were dependent on the composition of blend. The resin reinforced with low SBM contents (2.5 and 5 wt%) presented high values of flexural modulus and strength, while the blend reinforced with higher SBM load (10 wt%) showed higher elongation ability. This different behavior was explained by SEM analysis of fracture surfaces, which showed different toughening mechanisms. The adhesive strength and toughness were determined using carbon fiber/epoxy laminates with peel ply surface treatment as adherends. The results showed a dramatic enhancement of both properties for modified SBM/epoxy adhesives. The highest increases measured were 50 and 70% for lap shear strength and mode-I adhesive fracture energy, respectively.

The mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy after different solution treatments were investigated by means of Optical Microscopy (OM), tensile test, hardness and electrical conductivity tests, Differential Scanning Calorimetry (DSC), Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Results show that the tensile strength and hardness increase firstly and then decrease with elevating solution temperature when the holding time is kept for 30 min, and the maximum strength and hardness are reached when temperature is 520°C. The mechanical properties of alloy also display similar trend, which increase firstly and then decrease with increasing solution time when alloy is treated at 520°C. The tensile strength, hardness and elongation of the alloy solution treated at 520°C/30 min are 566 Mpa(σb),512 Mpa(σ0.2), 148HB and 8.23% (δ), respectively. TEM shows that an amount of T1 (Al2CuLi) phases are finely and dispersedly distributed in Al substrates, which can be an explanation of a mixed fracture mode of transgranular and intergranular delamination cracks observed by SEM.

(Na0.5Bi0.5)0.89Ba0.11 Zr0.04Ti0.96O3 (0.11BNBZT) ceramic were prepared by using solid-state reaction method. A single phase perovskite (ABO3) structure with tetragonal symmetry was confirmed by X-ray diffraction. The dielectric behavior, impedance relaxation were investigated in a wide range of temperature (30°C-600°C) and frequencies (45Hz-5MHz). The grain morphologies were analyzed by using a Scanning Electron Microscopy (SEM) analysis. The temperature dependence of dielectric behavior and the frequency dependence of impedance relaxation were investigated. A broaden dielectric constant peak were observed over a wide temperature range and also indicate a relaxor behavior. The complex impedance plot exhibited semicircle plot, which is explained by the grain effect of the bulk. The center of the impedance semicircles lie below the real axis, which indicates that the impedance response is a Cole-Cole type relaxation.

In selection and design of materials for tribological applications, high resistance to material damage or least surface deterioration of the contacting surfaces is of considerable interest. The present work deals with the study of the wear properties investigated under fretting condition of Al65Cu20Ti15 composite containing finely distributed intermetallic compounds, fabricated by mechanical alloying followed by pulse plasma sintering (PPS) process. The wear experiments were carried out in gross slip fretting conditions to investigate the wear performance of the composite against the Al2O3 balls with ambient conditions of temperature (24 ± 2°C) and humidity (50 ± 5%).

Intelligent foam has been achieved by blending epoxy and poly vinyl acetate (PVA) with different ratios, foaming with nitrogen gas was further performed. It was found 25 Kilo gray irradiation electron beam obtained from accelerator was enough for compatibility and modified mechanical behavior. Water uptake to 50% was maintained over night and release was completed after 6 days at 20°C. Thermal behavior testing revealed heat resistance up to 200°C. Structure characterization was determined by FTIR spectroscopy while mechanical investigation was applied using hardness tester. The Foam blend was used to trap alpha particles emitted by 239Pu and 241Am. Alpha counts were continuously recorded while water uptake was carried out until count cut off. Medium decontamination from radon was tracked via water uptaken foam using 773 ppm 226Ra source until count cut. Durability of foam was measured by ten times repeatable water uptakes alpha particles and radon cut off showed no significant difference. Radon associated lead and bismuth were determined in the foam using SSNTD CR39 and a streamer detector and assured by using EDX which proved sorption of radon by specified foam.

The study concerns the analysis of significant contact friction changes by changing the size of crystal grains in the processes of free axisymmetric work pieces upsetting, initial height of 2 mm. The friction changes result with significant changes in forming force. This phenomenon usually characterizes micro forming processes. Using hard experimental data in the creation of numerical FE (finite element) model, a dependence of the changes of contact friction in correlation to the change of the work piece crystal grain size for three different grain sizes: 39, 47 and 76 μm is presented. It is shown that the friction factor is increased by reducing the size of crystal grains. Physical interpretation of the results is given by theory of Bowden and Tabor.

Some glass factories have drilled and milled silica mixed with water, their treatment depends on precipitation, filtration etc. New concept for recycling of waste have paid attention to taking samples from different steps of traditional treatment, water evaporation of samples have been carried out. Investigation of attained powdered using EDX showed that, about 95.87% of sample was silica while particle size analyzer proved that it was not exceeding 73 micrometer. Silica powder mixed with Acrylonitrile Butadiene Rubber using miller and moreover thermal compression were performed to achieve maximum compatibility and constant thickness of the composite. Electron beam irradiation of the samples with different doses 25 and 100 KGy were carried out. Mechanical investigation using stress strain technique, showing that pure silica composite was more than waste silica composite of step one by small value. Thermal characterization was studied using thermal gravimetric analysis proved that improvement of the silica waste NBR composite than that of pure composite and also for electrical properties of the composite which have the same behavior. These results confirmed application of waste silica instead of pure one with NBR composites and management of environmentally problem such as water polluted with waste silica.

In this work, Poly o-anisidine nanoparticles was prepared by using cationic surfactant. Poly o-anisidine nanoparticles/ nanocomposites filled with constant content 1.0 wt% of Ag₂O, ZnO, CuO and TiO₂ powder have been prepared. The sample microstructure was established by FTIR spectroscopy and transmission electron microscopy. The thermal properties, sulfate reducing bacteria and electrical conductivity were investigated. The influence of the inorganic nanoparticles on the thermo stability of poly o-anisidine nanoparticles is very complicated. It was found that POA/Ag₂O nanocomposite microspheres have good effects to sulfate reducing bacteria than POA nanoparticle. The value of the electrical conductivity, σ, of the nanocomposites was investigated. It was found that the poly o-anisidine nanoparticles was improved by adding metal oxides which converted the polymer nanoparticles from insulator behaviour 10^-16(S/cm) to semiconductor behaviour 10^-11(S/cm) in case of POA/Ag2O and 10^-12 (S/cm) in case of POA/ZnO. The conductivity was increased by increasing the temperature.

A series of ZnO nanowire arrays were grown on seeded fluorine-doped tin oxide (FTO) substrates by hydrothermal method. The effect of reaction solution concentration on the length and morphology of ZnO nanowire arrays, as well as cell performance in dye-sensitized solar cell (DSSC) was investigated. It was found that with the increase of growth solution concentration, the ZnO nanowires became longer in length, but with the bottom of nanowires gradually interconnected to each other. The enlarged ZnO nanowire length lead to increased power conversion efficiency and achieved the highest efficiency of 1.54% with nanowire length of 8.6 μm; however, the further increased nanowire length and connected bottoms of nanowires restrained the further efficiency improvement due to the increased electron recombination and reduced surface area.