Beneficial Effects Of Si Research Articles

Enhanced mechanical response of hybrid alloy AZ31/AZ91 based on the addition of Si3N4 nanoparticles

► Si 3 N 4 nanoparticles were successfully integrated with hybrid magnesium alloy AZ31/AZ91 in extruded form. ► A simultaneous enhancement of tensile strength and ductility of hybrid alloy AZ31/AZ91 was observed. ► An enhancement of compressive strength of hybrid alloy AZ31/AZ91 was also observed. The main aim of this study was to simultaneously increase tensile strength and ductility of AZ31/AZ91 hybrid magnesium alloy with Si 3 N 4 nanoparticles. AZ31/AZ91 hybrid alloy nanocomposite containing Si 3 N 4 nanoparticle reinforcement was fabricated using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size to the monolithic hybrid alloy, reasonable Si 3 N 4 nanoparticle distribution, non-dominant (0 0 0 2) texture in the longitudinal direction, and 13% higher hardness than the monolithic hybrid alloy. Compared to the monolithic hybrid alloy (in tension), the nanocomposite simultaneously exhibited higher yield strength, ultimate strength, failure strain and work of fracture (+12%, +5%, +64% and +71%, respectively). Compared to the monolithic hybrid alloy (in compression), the nanocomposite exhibited higher yield strength and ultimate strength, lower failure strain and higher work of fracture (+35%, +4%, −6% and +6%, respectively). The beneficial effects of Si 3 N 4 nanoparticle addition on the enhancement of tensile and compressive properties of AZ31/AZ91 hybrid alloy are investigated in this paper.

Effects of Si on the Repassivation Kinetics and SCC Susceptibility of Stainless Steels

Effects of Si on the repassivation kinetics and stress corrosion cracking (SCC) of alloy 304Si were examined by a scratch electrode technique and slow strain rate test in chloride solutions and compared with those of other stainless steels (SSs), 304 and 316L. Repassivation kinetics of these alloys and alloy were analyzed in terms of the current density, , flowing from the scratch as a function of the charge density, , that has flowed from the scratch. Passive film initially nucleated and grew according to the place exchange model, and then grew according to a high-field ion-conduction model in which has a linear relationship with with a slope of . The repassivation rate of alloys, evaluated by the value, increased with an increase in Si content. Furthermore, repassivation rate decreased on the order of 304Si, 316L, and 304. The resistance to SCC of the SSs (304Si, 304, and 316L) measured in 35 wt % solution at was in good agreement with those predicted based on the repassivation kinetics. The beneficial effects of Si on SCC of 304Si SS appears to be associated with the enrichment of Si in the passive film.

Role of silicon in enhancing the resistance of plants to biotic and abiotic stresses

Although silicon (Si) has not been recognized as an essential element for plant growth, the beneficial effects of Si have been observed in a wide variety of plant species. The beneficial effects of Si are usually expressed more clearly in Si-accumulating plants under various abiotic and biotic stress conditions. Silicon is effective in controlling various pests and diseases caused by both fungi and bacteria in different plant species. Silicon also exerts alleviative effects on various abiotic stresses including salt stress, metal toxicity, drought stress, radiation damage, nutrient imbalance, high temperature, freezing and so on. These beneficial effects are mainly attributed to the high accumulation of silica on the tissue stirface although other mechanisms have also been proposed. To obtain plants resistant to multiple stresses, genetic modification of the root ability to take up Si has been proposed. In this review, the role of Si in conferring resistance to mutiple stresses is described.

オーステナイトステンレス鋼の孔食および間隙腐食におよぼすMo, SiおよびNの影響

Chemical pitting corrosion tests in neutral 1.0 M NaCl solution containing 0.5 M K3Fe(CN)6 and measurements of pitting potentials Vc′ and Vcre′ for stainless steel open surface and creviced specimens in 0.5 M NaCl solution were conducted to study the resistance to pitting and crevice corrosion of 18 Cr-14 Ni stainless steels to which the alloying elements Mo, Si and N had been added. The following results were obtained. (1) Mo and N increased the resistance to both pitting and crevice corrosion, whereas Si increased only the pitting resistance and had no effect on the crevice corrosion tendency. The beneficial effects of Si and N were found to be pronounced especially when 1∼3%Mo had been alloyed together with them. (2) In many cases, the pitting potentials of creviced specimens Vcre′ were found to be 0.3∼0.4 V more negative than those of open surface specimens. However, in the case of 18 Cr-14 Ni-3.5 Si-0.2 N stainless steel, Vcre′ was about 0.9 V more negative than Vc′, indicating a greater susceptibility to crevice corrosion. For practical purposes of assessing the susceptibility and/or resistance of an alloy to localized corrosion, it is essential that the pitting potential Vcre′ of the creviced specimen as well as that of the open surface, Vc′, be measured.