Band 114, Heft 6

The present work investigates the resistance of a progressively cold-drawn carbon steel wire against hydrogen embrittlement. In this study, analytical and numerical methods are used to determine the critical hydrogen content, the critical hydrogen ratio and the embrittlement indices of the different material conditions. The wire with the highest degree of cold deformation shows the highest critical hydrogen content and improved resistance against hydrogen embrittlement. At higher degrees of deformation, the material shows stronger hydrogen trapping, which improves in combination with a change in the lamellar spacing and orientation of the pearlite the resistance to hydrogen embrittlement.

Aluminum alloy wires with higher strength and better electrical conductivity are demanded in electrical engineering. Pre-torsion was employed to process aluminum alloy wire for the improvement of its properties. Uniaxial tensile and electrical tests show that simultaneous improvements of strength and electrical conductivity were achieved in the pre-torsioned aluminum alloy wire at a maximum shear strain of 0.27. Microstructural observations reveal that pre-torsion induces the formation of nanoscale rod-shaped β′ particles and the sizes of nanoscale precipitates increase with the maximum shear strain of pre-torsion. Based on the experimental results, a theoretical model is proposed to reveal the underlying mechanisms. The small nanoscale precipitates can contribute to the improvement of strength and electrical conductivity. The large size of nanoscale precipitates leads to the low strength and poor electrical conductivity. This is attributed to the weak strengthening and strong electron scattering in large nanoscale precipitates.

In this paper, for sintering silicon carbide nanopowders via the spark plasma sintering method, nano-and micro-sized alumina sintering aids were used separately at 3 vol.%, 5 vol.%, and 7 vol.%. The sintering process was undertaken at 1900 °C for 10 min. To investigate some mechanical and physical properties of the resulting samples, density was obtained via the Archimedean method, and hardness was taken by the Vickers indenter method. The microstructure of the samples was examined through scanning electron microscopy. The results indicated that in the samples containing nano-alumina, the largest percentage of density and hardness was related to the sample containing 5 vol.% nano-alumina as a sintering aid and were obtained as 99% of theoretical density and 31.3 GPa, respectively. For the samples containing micro-alumina, the highest percentage of density and hardness was related to the sample containing 7 vol.% micro-alumina and obtained 93% of theoretical density and 20.1 GPa, respectively. By investigating the fractured surfaces of the samples and via the linear intercept method, the largest mean grain size was associated with the densest sample at 3.7 µm.

Al 2 O 3 has received increasing attention in the field of cutting tools and structural ceramics owing to its good mechanical performance. The mechanical and thermodynamic properties of Al 2 O 3 matrix composites prepared by temperature gradient spark plasma sintering were investigated in this study. Liquid-phase sintering was confirmed to have occurred, based on thermodynamics and X-ray diffraction analysis during the fabrication of the Al 2 O 3 composites. By dynamically modifying the heating rate during the entire preparation process, Al 2 O 3 composites with smaller grain sizes were obtained. The effect of the tremolite additive on the hardness of the Al 2 O 3 composites was elucidated by comprehensively considering the hardness and densification effects. The microstructural evolution of the composites was analyzed. The critical crack length was considered as the parameter necessary to evaluate the thermal shock resistance of the Al 2 O 3 composites. The crack propagation resistance was found to significantly affect the thermal shock resistance of the Al 2 O 3 composites. The results showed that the thermal shock resistance of the Al 2 O 3 composites improved owing to the decrease in porosity and the improvement in mechanical properties due to the addition of tremolite.

The isothermal section of the Ti–Mn–Si ternary system at 600 °C over the whole composition range has been investigated by means of X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Twenty-five three-phase regions were identified. Four ternary compounds, namely, MnSiTi, MnSi 2 Ti, Mn 5 Si 4 Ti 2 , and MnSi 4 Ti, were confirmed in this work. Solid solutions of Mn 2 Ti with Mn substituted by Si and that of Mn 5 Si 3 with Mn replaced by Ti were observed.

The present research paper reports the structural, morphological and electrochemical properties of cerium oxide doped polythiophene nanocomposite. Polythiophene was first polymerized using the chemical oxidation polymerization method and further, it was mixed with an equal amount of cerium oxide (CeO 2 ) nanoparticles by mechanical mixing. The initially generated polythiophene sample exhibited an amorphous character according to X-ray diffraction investigation, however the PTh–nCeO 2 polymer nanocomposite displayed good crystallinity. The vibration bands of the PTh and PTh–nCeO 2 polymer nanocomposites were further examined using Fourier-transform infrared spectroscopic studies. The morphology and elemental composition of the prepared samples were investigated using scanning electron microscope and energy dispersive X-ray analysis. The electrochemical performance of PTh and PTh–nCeO 2 polymer nanocomposite was studied by cyclic voltammetry, Galvanostatic charge–discharge and electrochemical impedance spectroscopy measurements. The PTh–nCeO 2 polymer nanocomposites demonstrated a high specific capacitance of 161 F g −1 at a current density of 1 A g −1 among the produced samples. The Nyquist plot (low-frequency area) and Bode plot (phase angle) electrochemical impedance tests revealed excellent capacitive performance. The PTh–nCeO 2 polymer nanocomposites may be a good option for high-performance super capacitors, according to the findings.

In today’s world, wound healing is a growing serious problem for clinical institutes. In this study, nanofibrous scaffolds were prepared using polyurethane as a mat scaffold. Also, by immersing curcumin as an antibacterial component another scaffold was fabricated using the electrospinning technique. The obtained scaffolds were characterized by means of scanning electron microscopy, tensile analysis, porosity, and water vapor transmission rate. MTT and DAPI staining were used to prove the biocompatibility and cell attachment of the nanofibers. The curcumin incorporated into the PU scaffold can stop both the Gram-negative and Gram-positive bacteria activities through direct contact with them. Studies showed that the PU/Curcumin scaffold has considerable ability to play a key role in wound healing applications.