Materials Science Forum Vol. 1093

Abstract: The recrystallization and inhibitor precipitation behaviors of rare earths under water cooling after holding for different times of oriented silicon steel hot rolled at 1200°C in the ferrite zone with 30% deformation were analyzed using Gleeble 1500D, SEM,TEM and ICP. The results showed that: during the hot rolling of oriented silicon steel in the high temperature ferrite zone, only dynamic reversion occurred, no dynamic recrystallization occurred, and the amount of precipitates did not increase significantly; after deformation at 1200°C, static recrystallization occurred after holding for about 20s, and the inhibitor started to precipitate and grow. The higher the recrystallization rate, the faster the volume fraction of precipitates. After the deformation, the amount of Cu₂S and MnS in the precipitates was similar. At 64% recrystallization rate, MnS increased by about 8% and Cu₂S increased by about 23%. At the same time, most of the precipitates were precipitated in the crystal, and gradually nucleated and grew at the grain boundary when the holding time was extended. After rare earth lanthanum and cerium were added, the precipitation amount of inhibitor was reduced. The higher the degree of static recrystallization, the more obvious the effect of rare earth on the precipitation of inhibitor.

Abstract: Numerical modelling tools provide valuable means to quantitatively control thermomechanical processing. Several modelling tools have been applied and developed at University of Oulu during previous years, such as finite element models for hot rolling, recrystallization models, heat transfer and conduction model, coupled with phase transformation, as well as cellular automata and phase field models for simulating phase transformation during cooling. This article describes the overall development and recent progress of the developed numerical modeling tools.

Abstract: Theoretical ab initio calculations of the electronic structure were performed for the non-stoichiometric Mn_1.75Co_1.25Al Heusler alloy and compared with the electronic structure of the stoichiometric Mn₂CoAl full Heusler alloy. Both compounds are assumed to have the L2₁-type crystal structure in the calculations, the non-stoichiometry is taken into account as a substitution of a Mn atom in a supercell. The calculation for the non-stoichiometric composition of Mn_1.75Co_1.25Al showed that taking non-stoichiometry into account leads to a decrease of the total magnetic moment. In comparison with the inverse type of Mn₂CoAl, in both Mn₂CoAl and Mn_1.75Co_1.25Al, the metallic type of the total density of states at the Fermi level was obtained in our calculations. In Mn_1.75Co_1.25Al, the total density of electronic states is found to be close to the one of the stoichiometric Mn₂CoAl alloy in the majority spin projection, and in the minority spin projection spin polarization leads to the formation of the more intense peaks due to the appearance of an additional non-stoichiometric cobalt with a significant magnetic moment, as well as an increase in the magnetic moments of the other magnetic ions.

Abstract: Different types of fabrics, such as aramid, carbon, basalt, glass, and flax, as well as powder fillers, were used to manufacture the epoxy-based hybrid composites by the vacuum bagging method. In this work, the resistance of hybrid composites was examined in terms of their resistance to acts of vandalism, such as resistance to cuts with sharp objects, impacts, and flames. These technics were applied to determine the impact of the type of fillers and fabrics on the performance of hybrid composites.

Abstract: This paper explores the versatility of Bouc-Wen hysteresis model in simulating the dynamic behaviour of magnetorheological elastomer (MRE) material. Bouc-Wen model have been used in many field of science including modelling the hysteresis phenomenon happen in magnetic material, elastomer, base isolation of structures and many more. Introduced by the Robert Bouc, this nonlinear hysteretic model has been modified by many researchers to suit different applications. Compression testing of MRE material under high strain amplitude produces nonlinear hysteresis curve based on stress-strain data. Bouc-Wen hysteretic model has been found to be able to simulate the hysteresis curve of MRE material using parameter identification method within MATLAB Simulink.

Abstract: Physical and chemical approaches for synthesizing ZnO have disadvantages, such as requiring high temperatures, expensive equipment, and dangerous substances. Preparation of ZnO nanoparticles has shifted its focus to the biosynthesis technique involving plant extracts in order to support ecologically friendly activities. In this study, biosynthetic ZnO nanoparticles were produced using Sentul (Sandoricum koetjape) peel extract under two distinct microwave irradiation powers (i.e., 360 W and 720 W) for three minutes. The effects of microwave irradiation power on the morphology and optical properties of ZnO were investigated. Prior to microwave irradiation, Sentul (Sandoricum koetjape) peel extract (20g/l) and zinc nitrate hexahydrate (0.2M) as a precursor were mixed homogeneously. Morphological, structural, and optical absorption of the samples were characterized using field effect scanning electron microscopy (FESEM), X-ray diffractometer (XRD), and UV-Vis spectroscopy, respectively. Surprisingly, the surface morphology of ZnO displays geometric forms resembling flowers. Higher irradiation power resulted in uniformly smaller ZnO nano-flowers. The crystal structure of both ZnO samples is wurtzite with a hexagonal structure. Maximum light absorption occurs at 349 nm and 358 nm, respectively, for ZnO samples subjected to 360 W and 720 W of microwave radiation. However, the bandgap energies are 3.29 and 3.28 eV, which is significantly less than the bandgap energy of bulk ZnO. (3.37 eV). According to the results, it is possible to control the form and size of ZnO nanoparticles using microwave heating.

Abstract: Adsorption of gold from a solution in the form of gold nanoparticles (AuNPs) is a challenging approach. In this paper, Mg/Al hydrotalcite (Mg/Al HT) was functionalized with ascorbic acid (Mg/Al HT-AA) and applied to adsorb and reduce Au³⁺ to Au⁰. The anion exchange method was observed as a recommended way to immobilize and intercalate ascorbic acid to Mg/Al HT. Based on the TEM image, the formation of AuNPs was confirmed with the average diameter 16.3 nm. These findings suggest that Mg/Al HT-AA has a good potential as multifunctional adsorbent that can recover gold in solution and simultaneously turn it into gold nanoparticles.

Abstract: Targeted drug delivery systems with nanomaterials as drug carriers to specific organs can increase the therapeutic effect and reduce the side effects. Magnetic mesoporous silica nanoparticles are a multifunctional platform in drug delivery and magnetic hyperthermia therapy. In this study, the synthesis was developed with iron sand from Glagah Beach as a source for the magnetic nanoparticles formation and CTAB as a surfactant template. The research method was carried out in three steps, including the synthesis of magnetic nanoparticles (Fe₃O₄), coating of magnetic nanoparticles (Fe₃O₄@SiO₂), and surfactant-templating (Fe₃O₄@SiO₂@CTAB/SiO₂).The SEM analysis results showed that the Fe₃O₄ particles have various sizes. The weight concentration of Fe in Fe₃O₄ increased from 70.25% to 78.58% compared to Fe in iron sand by EDX analysis. The XRD results showed that the crystalline size of Fe₃O₄ and Fe₃O₄@SiO₂ particles are 6.31 nm and 2.37 nm, respectively. From the results of BET analysis, it is known that the longer sonication time, the pore diameter tends to decrease. It may be due to CTAB filling in the pore during the surfactant-templating process. The highest surface area of Fe₃O₄@SiO₂@CTAB/SiO₂ particle obtained was 14.31 m²/g with a pore diameter of 3.915 nm which has a mesoporous structure.

Abstract: We investigate the temperature-dependent resistivity (ρ(T)) and Hall coefficient (R_H(T)) of heavily Al-doped 4H-SiC and discuss the underlying conduction mechanisms. The sign of R_H(T) changes from positive to negative in nearest-neighbor hopping (NNH) and variable-range hopping (VRH) conduction, whereas it is positive in band conduction because Al-doped 4H-SiC is a p-type semiconductor. We propose a general physical model to explain why R_H(T) in hopping conduction becomes negative at low temperatures, which is applicable to both NNH and VRH conduction. Moreover, we elucidate why the activation energy for negative R_H(T) becomes similar to that of ρ(T) in NNH conduction.