Band 111, Heft 3

The role of a multiwalled carbon nanotube (MWCNT) network embedded in polymer nanocomposite is a key factor to study. Polyvinyl alcohol was used as the polymer matrix for 0.1 –0.4 wt.% functionalised nanotubes in an effort to establish the nanotube's role in nanocomposite films. The fabrication of nanocomposite film was conducted using an easy and simple procedure via the casting technique. Nanocomposite properties show that in the early addition of 0.1 wt.% MWCNT, an isolator–semiconductor transition with 1.1 × 10 −8 S cm −1 conductivity occurred. Nanocomposite films were shown to be sensitive to UV light at 250–400 nm and tended to have a high transmission (approximately ∼90 %) within the visible region. Additionally, an MWCNT concentration of 0.3 wt.% in the electron pathway carried charge carriers of approximately 2.1 × 10 −7 S cm −1 via a complete electrically-conductive path. As such, the network nanotubes displayed extraordinary properties as reinforcement for nanocomposite films when viewed in terms of mechanical strength and elongation increased in respective ranges of 7.3–18.8 % and 14.9–25.02 %. Upshift of the G-band occurred at approximately 7–26 cm −1 , which was indicative of an electron transfer between the nanotube and the matrix.

Fibers are widely used to reinforce polymer composites for various applications because of their mechanical properties and ease of manufacturing. Fiber reinforced polymers are being developed using synthetic fibers and natural fibers, including bamboo, bagasse, etc. The main goal of this work is to optimize the mechanical properties of bamboo mesoparticle/nylon 6 composites using a response surface methodology. The conditions used to achieve an optimal tensile strength, flexural strength, and impact strength were determined using a Box-Behnken design with three operational variables: alkali concentration, particle loading, and particle size. Based on the experimental design, experimental tests were conducted to develop a mathematical model and predict the mechanical properties of the bamboo mesoparticle/nylon 6 composites. The optimal conditions to produce a composite with a maximum tensile strength were achieved at an alkali concentration of 4 wt.%, a particle size of 1 μm, and a particle loading of 13.5 wt.%. The optimum conditions to produce a composite with a maximum flexural strength were achieved at an alkali concentration of 2 wt.%, a particle size of 1 μm, and a particle loading of 13.5 wt.%. Additionally, an alkali concentration of 4 wt.%, a particle size of 1 μm, and a particle loading of 9 wt.% produced a composite with the maximum impact strength. Overall, the results showed that the values predicted using the model correlated with the experimental values.

The Eu–Ga system is first optimized by the CALculation of PHAse Diagrams (CALPHAD) technique based on the experimental data in the literature. The associate model for the liquid phase is tested and compared with the substitutional solution model given the asymmetric shape of the liquid in the Eu–Ga phase diagram. Description results show that the associate model achieved better consistency with the available experimental data than the substitutional model. The liquid significantly deviates from the regular solution and shows association between Eu and Ga. The excess Gibbs energies of the solution phases (e. g., liquid, bcc, orthorhombic) are modeled through the Redlich–Kister polynomial functions. Intermetallics, such as Eu 5 Ga 3 , EuGa, Eu 2 Ga 3 , EuGa 2 , Eu 2 Ga 5 , and EuGa 4 , are treated as stoichiometric compounds. This work shows that the Eu–Ga system hosts two eutectic, five peritectic, and one congruent reactions. Two sets of parameters for self-consistent thermodynamic description of the Eu–Ga binary system are obtained.

The effects of minor Ce, Si and Ca additions on the microstructure and mechanical properties of the as-cast and T6 state AZ91 alloy were analyzed and compared in this paper by means of optical microscopy, scanning electronic microscopy, X-ray diffraction and tensile testing. Results showed that the addition of Ce and Ca could effectively modify the β-phase and the average grain size was refined from 239.7 ± 16.9 μm in AZ91 alloy to 57.8 ± 1.4 μm in AZ91-1.0Ce-0.5Ca alloy. Accordingly, the as-cast AZ91-1.0Ce-0.5Ca alloy showed optimum yield strength of 119 MPa and elongation of 10.7 %. Furthermore, AZ91-1.0Ce-0.5Ca alloy possesses a higher effect in the reduction of the discontinuous precipitates after aging and the yield strength increased to 164 MPa with elongation of 11.8 %.

Zinc phosphate particles are used in coatings that protect steel from corrosion. The corrosion of coated steel was examined at the microscopic scale in proximity of zinc phosphate flakes. The coatings were prepared by dispersing the zinc phosphate flakes in epoxy-phenolic resin matrix, spray coating on the steel substrate, and curing. Such prepared coatings were then scratched, and corroded in the artificial weathering conditions by means of a condensate climate test. The ongoing corrosion process was examined using environmental scanning electron microscopy (ESEM). By applying this approach, we observed the influence of the anisotropic particles of zinc phosphate on the formation of corrosion products. Local areas at the edge of the scratch that were in direct contact with the zinc phosphate aggregates, revealed the formation of a different crystal type compared to the plain areas of the scratch. The obtained data indicates that a partial dissolution of the zinc phosphate particles took place, and suggests that the influence of zinc phosphate on the formation of corrosion products was mediated by the presence of water.

This study investigated the in-situ formation of TiC–Al 2 O 3 and TiB 2 –TiC–Al 2 O 3 composite coatings on the surface of austenitic 304 stainless steel by the use of 3TiO 2 -4Al-3C and 3TiO 2 -4Al-B 4 C powder and argon arc cladding technology. The effects of pulse frequency 0–200 Hz on microstructure and mechanical properties of coating are studied. Microstructural study of coatings showed that the high cladding temperature triggered the self-propagating high-temperature synthesis of reinforcement phases TiC, Al 2 O 3 , and TiB 2 at the surface of 304 stainless steel. The use of pulsed current instead of direct current reduced the hardness of the coating by increasing the dilution. Also, in both groups of coatings, no significant difference was found between the hardness distribution over the coating layer in the specimens coated with pulsed currents at frequencies of 10 and 200 Hz.

High-entropy oxides (HEOs), due to their excellent physicochemical properties, have attracted extensive attention. In this work, the solution combustion synthesis approach was applied to prepare a series of porous single-phase HEO nanocrystalline powders. Equiatomic (Co 0.2 Cu 0.2 Mg 0.2 Ni 0.2 Zn 0.2 )O, (Cr 0.2 Fe 0.2 Mn 0.2 Mg 0.2 Zn 0.2 ) 3 O 4 and (Ce 0.2 La 0.2 Pr 0.2 Sm 0.2 Y 0.2 )O 2 were successfully obtained. While the former two could be stabilized into single rock-salt (Fm-3m) and spinel (Fd-3m) structures, the latter could be synthesized to have either CaF 2 -type (Fm-3m) or CaF 2 -related-type (Ia-3) structure depending on synthesis temperature. Furthermore, their chemical and microstructural homogeneity was further confirmed.

Al 4 SiC 4 powder was successfully synthesised at a temperature 150 °C lower than before: the use of a microwave hybrid heating method required only 3 % of the heating time compared to conventional methods. The effects of composition and processing parameters, such as temperature and dwell time on the formation process of Al 4 SiC 4 were investigated. The results indicated that with the excess Al from 0 to 5 at.% in the composition, the amount of Al 4 SiC 4 phase in the samples processed at 1 200 °C increased together with the decreasing amount of Al 4 C 3 phase. Further increases in the content of Al above 5 at.% resulted in the decrease of the Al 4 SiC 4 phase content. For a fixed composition of Al : SiC : C of 4.05 : 1 : 3, Al 4 SiC 4 formed as a major phase together with the decrease of SiC, C, and Al 4 C 3 phases at temperatures varying from 1 000 °C to 1 500 °C for 6 min. When the dwell time was extended to 15 min at 1 500 °C, a high-purity Al 4 SiC 4 phase with a tiny amount of impurities could be synthesised. The as-obtained powder was mainly composed of hexagonal plate-shaped particles with a mean diameter of approximately 1 μm.

In this study, the effect of adding granite powder and alumina to Al7075 for strength enhancement is discussed. Al7075-based composites were prepared by applying a stir-casting method. The microstructural analysis of the samples demonstrated that with an increase in the reinforcement percentage the grain size reduced. With the grain refinement, the hardness showed an increasing trend for 2 % and 4 % of Al 2 O 3 for a constant percentage of granite powder (2 %) and then showed a decreasing trend. For 4 % of Al 2 O 3 and 2 % of the granite powder, the tensile strength was increased by 33.6 % (183 MPa) and the hardness by 34.9 % (74.2 BHN). However, the corrosion resistance was decreased because of the presence of Fe 2 O 3 in the granite powder.

Organic–inorganic hybrid perovskite is currently one of the most promising photovoltaic materials. In the present work, CH 3 NH 3 PbI 3 nanowires were prepared by saturated vapor-assisted crystallization. The effects of annealing time on the size (width or height) and optical properties of CH 3 NH 3 PbI 3 nanowires were systematically studied. It was found that the width of nanowires first decreases and then increases with the increase in annealing time. Moreover, as the size of the nanowires decreases, the absorbance increases, but the transmittance and the band gap decrease.

A thermochemical treatment was developed to bioactivate titanium surfaces for dental implants. Titanium samples were roughened by acid etching in HCl/H 2 SO 4 solution and then autoclaved for 60 min in a bioactive solution. The sample surfaces were characterized using scanning electron microscopy, surface angle measurements, confocal scanning laser microscopy, and in-vitro testing. The results indicated hydrophilic sample surfaces and formation of sub-surface porosity after the thermochemical treatment. The treated surfaces also successfully induced Ca–P precipitation during in-vitro testing in simulated body fluid.